PLL: Why i think Alison (is still alive) and has a twin (theory)

READ!!! STORY: Allison was really popular, and then her Crazy twin sister, Courtney, who lived in a mental hospital, got jealous of Alison, and put on Allison's 'A' ring and pretended to be Allison. The Real Allison was then sent to the Mental Facility. The FAKE Allison (Courtney) became friends with The Four Other Girls (Aria, Hannah, Spencer and Emily) and had them tell her all their secrets and wrote them down in a diary. So then, their friend "Allison" was actually Allison's crazy twin Courtney. And the Fake Allison, Courtney, is dead, because her sister Allison got back from the mental hospital went INSANE and killed her sister Courtney, who was pretending to be her. "And yes I know the director said that it wasn't going to be like the books... but Mona became A, just like in the books. So I think they are going to say that she has a twin, but they are going to change it a little bit from the books" PLEASE REQUEST A VIDEO:)