"I'm a woman who has lived. I have plenty to hide."
-Salon of the Dead (5x20)
Diana appears in fourteen episodes.
In the season premiere Yes, Then Zero, Nate Archibald and Serena van der Woodsen attend a party at Diana's house in Los Angeles, California. While there, Nate practices Chuck Bass' new method for happiness: saying yes to anything he's asked. Diana approaches Nate and asks for a tour of the house after hearing him say yes to a question about whether he owns it. During the tour, they end up having sex in a guest bedroom. When it's over, Diana reveals that the house is hers and refuses to tell Nate her name. The next day, she tells someone on the phone that she was surprised to have met Nate so soon and before she got to New York. Immediately after, Nate shows at her house to collect his phone that he left the night before. She returns it and he leaves.
In Beauty and the Feast, Diana attempts to score an interview with Nate's mother, Anne Archibald, on her part in Howard Archibald's crimes and arrest. While there, she runs into Nate, who agrees to talk his mother into doing the article if Diana spends some time with him. Afterwards, Diana offers him an internship at her newspaper, The New York Spectator. He accepts, but soon suspects that Diana only hired him to have sex with her. To show him that she didn't, she offers to let him interview some high profile people at a fashion show. When they arrive, she asks him to question Congressman McCreedy about a recent trip to Mykonos. When he does, he accidentally outs the Congressmen for cheating on his wife. He realizes Diana set him up and confronts her. She explains that she isn't interested in being merely a newspaper, she wants to create a new gossip media empire. After he warns her that Gossip Girl already has that covered, they steal cell phones of guests at the show to find anything gossip worthy. After finding nothing scandalous, they come across a phone belonging to Ivy Dickens; the girl pretending to be Charlie Rhodes, Serena's cousin (The Jewel of Denial).
When Ivy finds out that Diana and Nate have her phone, she lies to get into the office to steal it back. When Diana notices it's gone after meeting her, she quickly figures out who stole it. She later calls and tells her that she won't out her secret if she comes to work at The Spectator as a reporter (Memoirs of an Invisible Dan). Soon after, The Spectator's launch is delayed after Gossip Girl reveals that Diana stole phones to get stories for the debut. In order to save face, Diana orders Charlie to find a big new story or risk being exposed. Meanwhile, Diana invites herself to the Waldorf's Seder for Yom Kippur, hoping to interview Blair Waldorf or Louis Grimaldi. While there, she meets Louis' sister, Beatrice Grimaldi. Diana quickly deducts that Beatrice is jealous of Louis impending fame and acquisition to the throne, and makes a deal with her to help her up her status quo if she gives an in depth interview on a royal feud. Their plan works out, and the next day when Charlie shows at the office with private files of the VDW's that Bart Bass collected (in season two), Diana sends her away; but not before she takes a photo of her younger self out of Bart's folder and burns it (The Fasting and the Furious).
In I Am Number Nine, Diana enlists Nate and Charlie to deliver invitations to her party for the paper that night. While delivering, Nate discovers that Diana is planning to attend the party with someone else. Annoyed of keeping their relationship on the down low, he decides to go with Charlie; who is trying to win a competition of Blair's to become a bridesmaid. Her final task is to score a kiss with Nate, which she does in front of Diana. Meanwhile, Diana helps Serena with a problem with her boss; although her solution gets Serena fired. She takes the opportunity to invite Serena to work at The Spectator, an offer she accepts. The next day, Diana puts a story on The Spectator about her relationship with Nate, making their relationship public. In The Big Sleep No More, Diana works to get more time to take down Gossip Girl, as she's taking orders from someone else. Meanwhile, Ivy's ex, Max Harding, comes to town and begins a fling with Serena. Diana decides to use this information to mess with Ivy before firing her.
Soon after, it's revealed that Diana is working for Nate's grandfather, William van der Bilt. He orders her to train Nate to take over within three days or she's fired, and being the major investor in the paper, he has the ability to do so. Diana lies to Nate that the board wants her to up their numbers in three days or she's fired. Wanting to help Diana, Nate asks Jonathan Whitney to help him hack into Gossip Girl's sources to make her readers lose confidence in her. He also tells Serena about the source site, and unbeknownst to him, Louis overhears. Serena advises him not to tell Diana, but he does anyway. When Diana sees that Nate has never sent anything to Gossip Girl, she realizes he really is a good man and decides to sacrifice her job for him. However, Louis, wanting to prove a point to Blair about her friends being toxic, uploads the site. When Nate finds out the site was uploaded, he realizes Diana must have done it. He goes to the office to confront her and discovers her meeting with William. She falsely confesses to uploading it and William offers to reinvest if Diana resigns her position to Nate, which she does. As a result, she leaves the paper and on her way out, informs William that if Nate were to ever find about what she does, they'll find the truth about him as well (All the Pretty Sources). In Riding in Town Cars With Boys, Chuck and Blair get into a major car accident. Chuck's uncle, Jack Bass, calls Diana to let her know what happened. After hearing that the damage was severe, she agrees to be on the next plane to New York and to meet him at the hospital.
Diana returns in It-Girl Interrupted as a new investor in the failing Spectator. While there, she toys with Nate and his relationship with Lola Rhodes. To get Diana out, Nate works with Lola to set Diana up with Lola's minor friend, Aidan, but they fail. After they're caught, Nate tells Diana he thinks she came back because she has unresolved feelings for him. While she denies it at first, she eventually admits to him that he's absolutely right. She apologizes for working with William behind his back and promises to stay out of his way. In Salon of the Dead, Dan and Blair decide to throw a salon to introduce their new relationship to everyone. Meanwhile, Diana learns that Chuck is trying to find a mysterious relative that saved his life after the accident, and she takes it upon herself to stop him from finding the truth. She also discovers that Serena is the current acting Gossip Girl and promises to help her keep the site if she helps her. Later, they both attend the salon and Lola, wanting to prove her theory that Serena is Gossip Girl, livestreams a conversation between Diana and Serena; during which Diana reveals she is Chuck's mother. Upon seeing the video, Chuck leaves the salon. She later goes to see him at The Empire and explains the whole story: she had an affair with Bart while he was with Elizabeth Fisher and ended up pregnant. When Elizabeth was unable to conceive, they decided to have Diana have Chuck and then leave town. But Elizabeth decided she was able to go through with raising another woman's child as her own and left Chuck with Bart. She finishes by saying that if Chuck wants a relationship with her, he knows where she is. She also apologizes for letting things get so serious with Nate and not telling Chuck who she was.
Soon after, Nate decides to dig into Diana and find out who is giving her money to finance The Spectator. He also becomes suspicious of her story after learning Jack was involved. He hires Chuck's PI, Andrew Tyler, who finds out that any record of Diana prior to a few years doesn't exist. Wanting to learn the truth, Nate reaches out to Elizabeth for any information; to which she responds with a photo of herself very pregnant a few days before Chuck was born, putting to rest any question about who Chuck's real mother is. But upon seeing the photo, Chuck notices that the arm wrapped around Elizabeth's pregnant belly is Jack's. He then begins to question who his father is (Despicable B).
In Raiders of the Lost Art, Nate seduces Diana to distract her while he steals her planner. He gives it to Chuck, who has Blair help him decode it. When Diana realizes her book is gone, she asks Serena to steal it back for her in exchange for Gossip Girl's cell phone number. Serena almost does so, but stops when she finds out the real reason the gang wanted it. Blair sends Dorota to massage the key to the code out of Diana, and they are able to determine that the codes are international area codes. They're also about to find out about a party Diana is hosting that night, and they get tickets to attend and find the truth. They then give Serena the book to give back to Diana; who is pleased and hands over the phone number. Serena and Lola trace the number to the location of the party, where they meet with Chuck, Blair, and Nate, and discover is a revolving brothel. Lola and Nate then go off to find Diana, or India, as everyone at the event refers to her as. When they find her, they blackmail her into leaving The Spectator or they'll release the info about her running a high class prostitution ring. Later that night, it's revealed that what Diana is really doing is hiding a still alive Bart.
In The Fugitives, Nate again tries to blackmail Diana out of The Spectator. She reminds him that she is still the main financial backer of the paper so if she's gone, the paper will be too. Meanwhile, Diana makes a deal with Chuck to help him get Bart out of hiding: she'll tell him the man who wanted Bart dead in exchange for Chuck getting her a clean getaway from New York. Chuck is able to work a way for her out by buying a newspaper in London for her to run, but Nate and Lola become angry that he's letting her leave without any repercussions. They tip off The New York Times to ruin her escape, and Diana then cancels her plans to help Chuck save Bart. However, the group still uses her girls to have the man, along with Andrew Tyler, an accomplice, arrested. Afterwards, Nate threatens Diana one more time. But she begs him not to ruin her chance at a new life, as she can't return to her old lifestyle and she never once lied about her feelings for him. Realizing that she is telling the truth for once, Nate decides to let her leave with her reputation in tact. Later that night, Lola asks Nate how Diana got away and he lies that he has no idea. He then gets a final text from Diana thanking him.
During the season finale The Return of the Ring, Diana sends Nate a USB drive containing security footage of the night of the brothel. On the tape, the real Gossip Girl is shown rooting through bags looking for the admin laptop.
"Now for the first time in my life, I feel like I belong somewhere." -Ivy
"But you don't. And when these people figure out you're not one of them, they're going to destroy you." -Memoirs of an Invisible Dan (5x04)
"Nate, can I add one more thing to your to do list?" -I Am Number Nine (5x06)
"I better head in. They called queen awhile ago." -The Big Sleep No More (5x07)
"You never did understand that sex sells."
"The editor in chief is chitchatting with his "bro" instead of working. And you wonder why the paper isn't doing well." -It-Girl Interrupted (5x19)
"I'm a woman who has lived. I have plenty to hide." -Salon of the Dead (5x20)
"Is that a threat? Because I am your main financial backer, and we did sleep together. Sometimes even in these offices."
"Thank you for what? Not telling me my father was alive, pretending to be my mother, or screwing my best friend?" -Chuck
"You mean, for keeping your father alive, for pretending to be your mother to protect, and, well, I don't expect you thank me for Nate. I suppose I should thank you for that one." -Diana
"Nate, I made several bad choices early on in life but I wanted to escape that world and start fresh. The Spectator is my shot at doing that, and being here with you, is the happiest I've ever been." -Diana
"I don't believe you. You lied to me from the moment we randomly met in Los Angeles and you're lying to me now." -Nate
"I never lied about my feelings to you. I think in your heart you know that. Nate, I can't go back to my old life, and I stand no chance of starting a new one with my name in the headlines. Must you keep me here to humiliate me on top of that?" -The Fugitives (5x23)
- She has lots of influential contacts all over the world.