Emily

* In Pretty Little Liars, Mona is A in the beginning but is killed por falling off a cliff (when trying to push Spencer off) but in the end Ali becomes the real A. Ali never died and is actually a killer. Alison has a mentally ill twin named Courtney that none of her friends knew about. Courtney escaped from a mentally ill center, pretended to be Ali, and had her sister sent to the center saying Ali was Courtney. Courtney read Alison's diary containing all the girls secrets. When Alison escaped from the center, she sneaked into the celeiro and kidnapped her sister and buried her alive in revenge....