Maureen is introduced in Seder Anything when Blair and Nate attend Tripp and Maureen's wedding rehearsal and dinner. Blair is counting on Maureen to get her into any number off charities to help boost her social climbing agenda. After she's passed over for the Junior Whitney Committee for one of Maureen's bridesmaids, she makes a deal with William van der Bilt to convince Nate to go to Yale University if she can be one of her bridesmaids. In The Grandfather, she meets Vanessa at the van der Bilt compound and admits her first time there was intimidating too but she shouldn't worry about Nate's future, as William will take care of creating it.
In The Grandfather: Part II, Tripp is running to be a Congressman but is losing in the polls on the morning of election day. While taking a walk with Nate, a man falls into the Hudson River and Tripp saves him, ultimately boosting his numbers. Vanessa catches the whole thing on tape and figure out it was a hoax. When Nate and Tripp find out, they confront William, the obvious coordinator, and begin to alienate him as punishment. After Tripp wins the election officially, Maureen reveals to William that she was behind the set up and not only is Tripp a Congressman, he is out of William's control.
Maureen returns in The Last Days of Disco Stick, as she and Tripp are about to make the move to Washington DC. She asks Serena to help Tripp pack their home office, as it has sensitive family information. While she's gone, Anne Archibald reveals to Tripp that Maureen was behind the Hudson River scandal, causing Tripp to rethink and question his marriage. This is the start of his affair with Serena. In The Treasure of Serena Madre, Lily van der Woodsen invites Tripp and Maureen to their Thanksgiving dinner after bumping into her on the street. Jealous of their affair, Nate offers to help Maureen expose them once he gets a tape of them together via The Empire's security cameras. After she confronts the both of them, Tripp decides to leave Maureen for Serena and they leave together. Later, Maureen comes back for her coat and accidentally takes Lily's, which is identical to hers, and discovers a letter from William van der Woodsen, with proof Lily cheated on Rufus Humphrey.
In The Debarted, Maureen makes her last appearance when she meets with Tripp about next steps. She says she's willing to let him be with Serena, so long as Maureen gets to continue being his wife in public. Tripp hesitantly agrees, and Maureen asks to talk to Serena privately. At their meeting, she reveals that she has the letter William wrote and will use it against her and Lily if she doesn't know and stay in her place. However, Maureen shows Rufus anyway. Angry that Tripp told Maureen where she was and lied about where he was, Serena demands he take her back to the city. On their way back, they get into a car accident which leaves Serena injured. Tripp abandons the scene and when confronted about it by Nate, Maureen says Tripp will not be held responsible as he has an air tight alibi that he was with her all night.Rhodes to Perdition, the first story he's given has to do with Tripp and Maureen. There's a rumor that Maureen is cheating on Tripp with anyone and everyone. However, he later discovers Maureen is lying about the affairs. In Father and the Bride, Nate and Serena find out Tripp was behind Chuck and Blair's car accident (Riding in Town Cars With Boys), and that he meant for Nate to get hurt. Tripp tries to pin it on Maureen, but Nate and William figure he would never admit guilt and try to blame someone else. William reveals that Maureen couldn't have done it because they were together that night, meeting with divorce lawyers.