What are some things that Cassie must take stand on? Why?

Cassie takes a stand on Lillian Jean's treatment of her. She becomes her friend, learns her secrets, and then beats her up.... careful not to leave any marks. In this, she is standing up for herself. I'm not sure her parents would approve, nor an I sure that I approve. Cassie, none-the-less, solves her own problem with minimal damage.