Make Friends Break Friends by Julia Jarman
Daisy has two best friends, Phoebe and Erika, but they don't get on. Erika thinks Phoebe's feeble and Phoebe thinks Erika's a bully. Daisy has a plan to get her two best friends to like each other, but suddenly everyone is against her! Then the three girls have to spend a night together in a spooky old mill . . .