My Name is Evil (The Nightmare Room, Book 3) by R. L. Stine
You hold in your hand the key to a shadow world of shivers and screams. Take a step away from the safe, comfortable world you know. Unlock the door to terror. There's always room for one more in... THE NIGHTMARE ROOM!
When Maggie goes to a carnival fortune teller, she is told that she is EVIL... Maggie thinks it's all a joke, but when evil things start happening at school, Maggie gets the blame. What if the fortune teller is right?