|“||It was a headache. Why? You sorry it wasn't a tumor?||”|
— Addison to Emily
She is introduced as a member of the school swim team and a thorn in Emily's side. After Addison misses swim practice and makes up a fake excuse, Emily attempts to discipline her. Addison, in turn, tries to get Emily fired by making up a story of how Emily was hitting on her and several of the other girls on the team. She tells Paige, thinking that she'll side with her, stating that she is now being harassed and punished for not responding to Emily's advances. After finding out about Addison's allegations, Emily confronts Addison. She calls her out on her fake excuse, stating that she was hanging out with a boy as opposed to being sick. Before things could escalate further, Paige intervenes with evidence of Addison's attempt to fire Emily and sends the girl to Principal Hackett's office.
One year later, Addison is still up to her bullying habits among students and teachers. Her friends are afraid of her, but Jenna Marshall is able to scare her into submission. One night at a sleepover, her friends wake up wonder where she disappeared to with Willa. When Willia returns, she states she may have heard her scream, thus ending the series full-circle.
- She is the new version of high school Alison DiLaurentis, as of Till DeAth Do Us PArt.
- She is described as a pretty little bully who’s attractive, entitled, manipulative and intimidating, and every insecure high school girl’s worst nightmare.
- She is on the Rosewood High swim team and in Alison's English class.
- Emily used that tape to blackmail Addison to stop spreading rumors about her.
- She is somewhat homophobic, as she refers to Alison as a "lesbo" in Till DeAth Do Us PArt.
- She's currently missing, and the circumstances around her disappearance are unknown.