Mona Vanderwaal is Hanna Marin's best friend. Ever since Ali dissapeared the two began hanging out. Back then they both had something in common, they were both unpopular. Mona and Hanna made a pact to become prettier, lose weight, and to be the most popular girls in Rosewood Day High School. Once that was accomplished, the two just seemed like normal BFF's. They went shopping together, did eachothers make up, and even made fun of those who thought they had a chance to hang out with them. But, Mona has another side to her. In the books she was the pain the girls have had to deal with for the past few weeks, A. She had a second phone with a blocked number to text the girls with. In the fourth book the girls make a shocking discovery as to Mona being A. Her and Spencer have a little fight before Spencer accidentally pushed her off of a cliff into a rough river below. That was the last they had ever seen of Mona.
-A