Dark Room by Tom Becker...*

When Darla and her feckless dad, Hopper, move to Saffron Hills, Darla hopes it'll be a new start for the both of them. But she stands no chance of fitting in with the image-obsessed in-crowd at her new school. Then one of her classmates is brutally killed when taking a photo of herself. A murder Darla herself predicted in a bloody vision. When more teens die in a similar fashion it appears that a serial killer is on the loose - the 'Selfie Slayer'. Darla alone is convinced that the murderer might not be flesh and blood...*