The Misper by Bea Davenport

I knew this girl, you see. A sort of a friend. No one thought she really mattered much, but that turned out to be a mistake. Because she blew a hole through my life - and the lives of everyone I knew.
Anna's found the perfect friend in Zoe: she's cool, she's smart, she's goth, she's gorgeous. If only geeky Kerry would stop hanging around and cramping their style. They'd like to get rid of her. But they should be careful what they wish for...
The Misper by best-selling crime and children's writer Bea Davenport is a gripping story of obsessive friendships, jealousies, bullying - and the consequences of your actions.