Mona Vanderwaal

Mona Vanderwaal is a fictional character and one of main antagonist's (currently a protagonist) in the Pretty Little Liars series by Sara Shepard. She is portrayed by Janel Parrish in the ABC Family television adaptation.

Character
Mona is a former unpopular girl at Rosewood who longed to be accepted into Alison DiLaurentis's group and was continuously mocked by Alison. After Alison's disappearance, Mona befriended Hanna Marin and they underwent an "extreme makeover" together; as a result, they both became popular students. When "A" appears, Mona becomes jealous of Hanna rekindling her friendships with the other Liars.

Season 1
Mona is one of Hanna's close friends. When Alison was around she was a loner and tried to become friends with Alison and her clique but Aria, Emily, Spencer, and Hanna did not talk to her because of Alison's influence. Soon after Alison's death, Mona came into the in crowd and became a close friend of Hanna's. Though Mona means well she ends up messing somethings up for Hanna such as not giving or even telling Hanna about the love letter that Caleb wrote for her before he left for Arizona.

Season 2
She becomes romantically involved with Noel, much to Hanna's disapproval, but is later dumped by him for Jenna. When "A" begins sending Mona threatening notes, she grows closer to the Liars. When Mona and Spencer travel to the Lost Woods Resort to uncover "A"'s lair, Spencer starts to realize Mona is "A". After Spencer put the pieces together Mona hits her over the head, when Spencer comes to she is in the car with Mona. Mona tells Spencer she admires her and gaves her a choice to either join the "A" Team or disappear. Aria calls Spencer and realized Mona was holding her captive and Spencer tells Aria that they are going to Lookout Point, the Liars race to meet with them before Mona can hurt her. Spencer starts asking Mona why she was doing this to them she thinks it's because of Alison but Mona tells her it was because they stole Hanna away from her. While Mona was distracted Spencer pulled the emergency brake and they stop she runs out of the car and the Liars are coming straight for them at full speed Hanna is driving and Emily and Aria yell at her to stop the car before they hit Mona but she doesn't til the last second a stunned Mona screams and rushes to attack Spencer they struggle and then Mona falls off a cliff. The police arrive and Mona is found alive, she then is committed to the Radley Mental Institution, after being diagnosed with borderline personality disorder. It is subsequently revealed that Mona had been taking orders from an unknown person.

Season 3
Although at Radley, Mona gives answers to Hanna concerning Maya's death. Unbeknownst to "A", she secretly gives Maya's website to Hanna in code, leading the liars to eventually discover that Nate killed Maya. It is later revealed that she began the A-Team herself along with Toby, but then a person in a red coat came along and changed the game, taking control over the A-Team. Mona later reveals she actually doesn't know who "Red Coat" is, and is basically expelled off the team for letting Spencer and Toby trick her. At the end of season 3 it is revealed Alison is 'Red Coat". Mona then gets a text along with the rest of the girls in red font: Your mine now. Kisses! -A, implying she is now a victim of "A".

Season 4
Mona appears to be somewhat cooperative to the liars, since she now, is a victim herself. This includes giving Hannah the video of her mom running over detective Wilden, and telling them things such as it was Lucas who gave Emily the massage, and how Melissa was oin the Halloween train with Wilden, also she believes that Shana is in love with Jenna, and they both are afraid of Melissa