Yeah I didn't really fully get the whole ending. I don't understand the Audrey role in it all. First of all why did Audrey kill Piper before Piper was able to kill Emma and her mom if she was in on it. Then why would Audrey kill the girl she supposedly loved? Then why would she kill Riley who was her friends Noah's girl. To me Audrey had no motive to kill anyone but Nina so I really don't understand her involvement in it all. Then Piper being the killer was okay I guess it was a bit predictable towards the end and not the best angle in my opinion as far as angry daughter who wants revenge on her mother and sister but not all that bad either. The part that bothers me is how Audrey fits in because I feel like they are going to have a hard time explaining that one.
I think Audrey had piper kill rachel because Rachel had the video of Audrey threatening to kill Nina & she didn't want anyone to find out. I think they both did it out of revenge. Piper killed all of Emma's friends to make her suffer, & I think Audrey helped cause she was pissed that Emma stopped being her friend.