This is my theory on Jessica and Mary Drake.

NOTE: This is a THEORY let me know what bạn guys think..

Obviously the twin theory also exists in the hiển thị (like in the sách only it's not Alison/Courtney) it's Jessica and Mary.

1. So Mary told Spencer that Jessica was jealous of her (like Alison was of Courtney) they never got along, and always fought. Mary was in Radley when Spencer was born. (Possibly Charles/Charlotte/CeCe as well I can't remember) In the books, Alison had a mental disability but made everyone think it was Courtney. Who is to say Jessica didn't do that as well to get rid of Mary?...