In You've Got Yale!, Serena introduces Dan to her new Shakespeare teacher, Rachel. Meanwhile, Blair discovers that Yale has rejected her early acceptance application. When she confronts Headmistress Queller about it, she learns that Yale offered an early acceptance to another Constance student but if they decline, she's next to receive the offer. Later that morning, Blair gets a graded paper back from Rachel that received a B. She tries to intimidate Rachel into changing the grade so she can keep her GPA perfect, but Rachel refuses to do so. That afternoon, Serena reveals to Blair that she was the one who was offered the spot at Yale but she turned it down to help Blair. However, Blair is still angry at Rachel for giving her a B and decides to haze her to teach her a lesson. After obtaining her cell phone number, she invites her to have dinner with her family and then attend the opening night of the opera. Rachel accepts, but quickly realizes that Blair invited her to a closed restaurant and lied about what time the curtain was. Before the opera can begin, Blair receives a call from Headmistress Queller, who tells her that Rachel spoke with her about her concerns on not getting into Yale; and that she truly cares about her students. Realizing she made a mistake, Blair goes to apologize and does, but Rachel tells Queller about the incident anyway. The next day, Queller gives Blair detention as punishment and that Yale has put her acceptance on hold until she completes it. Meanwhile, Rachel strikes up a friendship with Dan.
After completing detention, Blair decides she wants to get Rachel back for telling on her. She enlists Nelly, Hazel, Isabel, and Penelope to help but they don't agree to help until Constance reveals a new policy, spearheaded by Rachel, to not allow cell phone usage during school hours. They search for any and all dirt on Rachel but can't find anything worthy. However, Blair finds her smoking gun when she sees Dan awkwardly interact with Rachel, and tips off Gossip Girl that the two are having an affair. Serena tells Rachel about the rumor and Gossip Girl, and Rachel informs Queller about what happened. They quickly identify Blair as the source, with the help of Dan and Nelly; who told on Blair to save her own record. As a result, Blair is expelled from Constance. The next day, Blair's father, Harold, asks if the rumor is true and she promises that it is. He decides to fight the expulsion and calls an emergency parent meeting at the school. Meanwhile, Serena has become increasingly uncomfortable with Dan and Rachel's budding friendship but meets with Rachel to ask her to give Blair a second chance. Rachel refuses and leaves, accidentally leaving her planner behind. Serena finds that she has a dinner date that evening and plans to intercept her to return the planner. Once she arrives, she finds that Rachel is having an intimate dinner with Dan and she takes photos of the two hugging and him pushing a lock of her hair out of her face. Hurt, she shows the photos to Blair; who hurries to the parent meeting to back up her story of the affair. Once the parents see the photos, they vote to fire Rachel and reinstate Blair at Constance. However, Blair accidentally reveals to Harold that she did lie initially and just happened to get evidence that backed her up. Upset that Blair lied to him, Harold returns to Paris. Meanwhile, Queller reveals to Lily and Rufus that the board believes they didn't have enough evidence to fire Rachel and she could sue for wrongful termination, so she will be allowed to resume her job. At the same time, Dan and Rachel sleep together, as she believes she is no longer employed at Constance (Carrnal Knowledge).
In The Age of Dissonance, Dan notices that Rachel is ostracized by other members of the faculty and asks Jenny to pass a note to her, inviting her to talk with him. She writes back and includes a key to her place, but Rufus intercepts the note and orders her to stay away from Dan. On opening night of The Age of Innocence, Dan and Rachel hook up in the costume closet. Meanwhile, Blair is officially rejected from Yale and searches for the person who outed her hazing of Rachel to the school. Dan eventually finds out that Rachel was the one who told Yale and confronts her about it. She doesn't deny it and he tells Blair what she did, as well as that they had sex in the costume closet. She apologizes to Blair and admits to hooking up with Dan. Later that night, she leaves Dan a note saying that she is returning to Iowa.
- Teaching at Constance Billard School for Girls was her first salary job.