The Tulip Touch by Anne Fine

Nobody wants Tulip in their gang. She skives off school, cheeks the teachers and makes herself unpopular with her classmates by telling awful lies.

None of this matters to Natalie who finds Tulip exciting. At first she doesn't care that other people are upset and unnerved by Tulip's bizarre games, but as the games become increasingly sinister and dangerous, Natalie realises that Tulip is going too far. Much too far.

Racing, in fact, to the novel's shocking ending.