Janel Parrish portrays Mona Vanderwaal, the original and first "A ''. She is the person who stalked Alison before her disappearance, and did this as revenge for Alison crowning her "Rosewood 's biggest loser ''. After Alison disappeared she became best friends with Hanna Marin and they transformed themselves into the most popular girls at school, taking Alison 's place. In the season two finale she is exposed as "A '' and sent to Radley Sanitarium, where she is visited by CeCe Drake (Charlotte), who takes Mona 's place in the "A '' game. In Season 3, she continues working as "A '' and by the end of the season is kicked off the "A '' team and becomes a victim of "A '' along with the other girls. In Season 4 she helps the girls out with their investigations of the new "A ''. In season 5 she creates an army so as not to be intimidated by Alison 's return. Later in the season, she fakes her own death to ferret out "A '' but is kidnapped by "A '' and imprisoned in "A '' 's dollhouse. After the time jump, Mona is working for Veronica Hastings ' rival for State Senator, and is revealed to be Charlotte Drake 's killer.
who is an a in pretty little liars
Mona Vanderwaal