NOTE: This is a THEORY let me know what you guys think..
Obviously the twin theory also exists in the show (like in the books 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?...
We’ll be looking at the most questionable fashion choices the girls of “Pretty Little Liars” have made throughout the years. Our countdown includes the girls' funeral outfits, Mona's polka dot outfit, Aria's mixed prints, and more!