An episode they could have done in 5B:

Interesting. If we take the things we know about the story as given (characters, behavior, secrets), we have to consider a lot of things.

Ali would create Mona, but she would be still mean to her (like she was mean to the others). The liars would have a different relationship with Mona. Aria and Emily wouldn't have much contact to her, Spencer and Mona would fight and hate each other, Hanna would be okay to her.

Mona would try to befriend Hanna again by trying to help her and by being nice to her. Hanna would get stronger and does whatever she likes to do. Ali would fight this because that's how she controls Hanna and would be mean to everyone. She would force them to do mean stuff to other people. She would expose the girls. Mona would start to blackmail Ali. Ali would go more crazy and trusts no one, she wins Aria and Emily on her side, but Spencer is skeptic about the fight and starts to focus on school. She would take drugs again and Ali would start a war on Spencer, because no one leaves Ali. Ali would start to blackmail Spencer at this point, because she thinks that maybe she is blackmailing her. Emily would be very quiet but on Ali's side. She would never tell that she likes girls because Ali would hold her down to have control over her. Aria would be on Ali's side too because she trusts her and Ali would use her father's affair to control her. Ali would try to expose secrets about Spencer, Hanna and Mona, because she needs them to play the game and because they hurt her. Mona would try to win the school on her side at this point and will show the pretty side of her face, but the other side would show how she tries to open up the DiLaurentis' secrets and there are a lot of them. Secrets, Ali don't know about and memories someone made her forget. Mona would blackmail Ali with very dark secrets and Ali feels fear rising up. She would make her holidays far away and tries to get close to new people and make new friends, friends that she can use for an escape, because Ali feels trapped. Then she decides to fake her death and run.

What I want to say is that I don't think that Mona and Ali could be friends. Not in season one or before season one. They only could be friends if they have a very great secret together or if they need to bond to fight someone else.

What do you think? The story above is just one end of a causal chain.

/r/PrettyLittleLiars Thread