Headmistress Queller makes her first appearance in School Lies as the new Headmistress at Constance. She is responsible for punishing students who attended the illegal pool party on school grounds and intimidates each separately until Serena van der Woodsen finally takes responsibility for the party. However, Bart Bass is able to talk Queller down to only issuing community service as punishment rather than expulsion.
Queller appears again in The Serena Also Rises when Jenny Humphrey is caught skipping school for two weeks. She calls Rufus Humphrey for help when Jenny tells her she isn't coming back to Constance. In You've Got Yale!, Blair Waldorf demands a meeting with Queller when she isn't given an early acceptance to Yale. Queller assures her that Dean Berube told her that Blair is next in line if their first choice declines, but then later informs Yale when Blair hazes new teacher Rachel Carr. She sentences Blair to detention and informs Yale when she has done so. Once she learns that Blair started a rumor that Rachel is having an affair with Dan Humphrey she expels Blair, but reinstates her when Blair provides proof that she was telling the truth. The parent committee votes to fire Rachel but Queller ultimately decides not to, as the board believes they don't have sufficient evidence to oust her (Carrnal Knowledge). Later, Rachel anonymously tells Yale what Blair had detention for and she is denied admission to the school (The Age of Dissonance).
Headmistress Queller returns in the finale The Wrong Goodbye at the Constance-St. Jude Alumni Fundraiser event. She tells Serena that she's surprised she never left New York, and that she was tough on her in school so that she would be more inclined to succeed. She also admits that she wishes Serena had left her life in Manhattan behind to explore the world.