Alison DiLaurentis is one of the main characters of the book, even though she went missing three years ago—when she was in seventh grade—and is found deceased at the end of the book. However, the stories of the four other central characters—Spencer, Aria, Emily, and Hanna—revolve around their former friendship with Alison and the secrets that she knew about them. Alison is the glue that bonds them all together.

In seventh grade, before she went missing, Alison was “perfect” (3) with blond hair that she sometimes wore in a ponytail. She was “Beautiful, witty, smart” (3) and popular. All the boys liked her, and the girls were jealous of her and “wanted to be her” (3). She played field hockey and was the only seventh grader to make the Junior Varsity team. She would ride home with the older girls and smoke cigarettes with them.

One of Alison’s defining qualities was that she was “so mean” (57). While the other girls were also mean, Alison was the worst. After she disappears, the girls are upset but they also feel somewhat relieved. They loved Alison, viewing her as “the shoulder to cry on” (18), but “they were also afraid of her” (18). A lot of their memories of her involve her bullying, disrespecting, or shaming them.