Answer
Mona Vanderwaal, portrayed by Janel Parrish, is a complex character in "Pretty Little Liars." Initially introduced as a timid and awkward outsider, Mona's true nature is gradually revealed as she becomes entangled in the Liars' secrets and torment. As "A," she orchestrates elaborate schemes to manipulate and control the group, driven by a desire for revenge and a twisted sense of justice.