Lola Quincey, the fifteen-year-old cousin of the Tallis children, wants to be grown up. She's a drama queen who paints her toenails and wears perfume with a "womanly tang" and steals the main role in Briony's play while acting like she's too good to be in the play anyway (1.10.20). She has an invincible egocentrism that she inherits, apparently, from her mother—an "obliviousness to anything beyond her own business" (1.1.53) that enables a thoughtless cruelty. If she were your cousin and came over to your house and stole the lead role in your play, you probably wouldn't like her very much and we'd totally understand.
And yet, Briony does like her, at least sometimes. Lola's parents are divorcing and she needs a friend. When she comes to Briony in distress supposedly following an attack from her twin brothers, the younger girl comforts Lola and shares a secret with her. And when Briony finds Lola after she has been assaulted, Briony feels tenderness toward her wounded cousin. In other words, Lola isn't just a bully—she's also a victim.
Both times that Lola is attacked Paul Marshall is her assailant, and both times other people are blamed. The first time Lola blames her brother, and the second time she sits silently while Briony blames Robbie. We never really learn why Lola lies to protect Paul, though we do know a few things about the situation:
But why Lola does these things we're never told. If Briony has a gift for telling tales, Lola has a gift for not telling them. "I couldn't say for sure," she tells Briony after her rape, and she keeps right on not saying for the rest of her life (1.13.44). For Lola, growing up seems to mean keeping silent and, in that sense, she's the anti-Briony—the character who shows that not telling stories can be as cruel, and as painful, as telling them.