Where is Ali on Pretty Little Liars?

Answer 1

Alison DiLaurentis has a secret twin sister named Courtney DiLaurentis who has been shipped away to a mental hospital. Only her family knows about her. Alison is living a happy life in Rosewood until 6th grade when Courtney visits. She pretends to be Ali and steals her "A" initial ring. When it's time for Courtney to go back, they don't know who to believe is actually Ali because they are both saying they are, so they accidentally ship the REAL Ali back to the mental hospital. After this, "Ali" who is actually Courtney befriends Aria, Emily, Hanna, and Spencer, because she knows nothing about the REAL Ali's old friends. They are happily friends until that night on the last day of seventh grade when, that weekend, "Courtney" comes to visit. So when "Alison" goes to the sleepover, "Courtney" is at her house. When "Ali" slips away after her fight with Spencer, "Courtney" comes out and kills her for revenge. So then in all that chaos and mayhem, "Courtney" goes back to the mental hospital that weekend. That is how it is in the books, but supposedly they are changing it in the TV show.