What happens to Mona in Pretty Little Liars?

Answer 1

A lot. She was Loser Mona, then she became popular. Then she became A. She then got caught and eventually became friends with the liars. She goes to Radley and goes literally insane. She finally goes back to being A so she won't get tortured and then she teams up with the liars to find A.

Answer 2

She tried to kill spencer. But then Spencer and Mona start fighting. She accidently falls off a cliff during the fight.
A lot. Basically she was a loser then she became a prep. She then became part of the A team and when she got caught she went crazy but secretly was still A. When she got out, she gave up and helped the liars figure out the leader of A.