Thirteen Reasons Why
by Jay Asher
Who doesn't love Courtney? Well, Hannah, for one. Number five on Hannah's list, Courtney is the pretty, sweet girl at school. But Hannah thinks she's a phony: Courtney only pretends to like Hannah when she needs something, like a ride to a party or an adventurous night of let's-catch-the-Peeping-Tom.
Courtney betrays Hannah by inventing a story that Hannah keeps sex toys in her dresser. Courtney's betrayal contributes to Hannah's belief that nobody around her is even slightly trustworthy.