2x12 - "Over My Dead Body"

So mona is A and then spencer figures it out and mona tries 2 push her off a cliff. Then mona falls off and dies so all the girls think they r done with a well they r not. It turns out tht ali had a secret twin sister she never mentioned so then her parents tell everybody in town bout courtney. But it turns out tht Ali was really courtney so courtney died tht night. So the other sister who is rlly ali is still alive. But in 6th and 7th grade it was courtney not ali. So ali killed her cause courtney forced her to go to this medical hospital instead of her so ali came back and killed her but they had the same dna so it could of been an easy murder. So then ali makes vrienden with all of them and then takes them to the lakehouse and sets the house on brand and tells them but instead of them getting killed ali did. Oh she also kidnapped melissa and killed ian cause he waz on to her. She also killed jenna because jenna knew and she waz goin to tell the police so that is the ending.