You Were What You Eat by Stephanie Prochaska
As a vampire, Anna Ellington knows about hunting. She knows how to find isolated prey, how to put people at ease, how to leave no trace behind. What she doesn’t know about is high school. Students don’t pay attention, her English teacher repeats the same lesson for days on end, and why does she seem to be the only one not bolting for the door when the bell rings?
With one friend who’s obsessed with vampires and another who’s not quite what she seems to be, Anna has to learn the rules of high school fast if she wants to remain undetected. As attacks throughout the city increase, suspicions mount. Anna tries to go unnoticed, but when her newfound friend sets out to prove the attacks are being caused by a vampire, Anna is left to wonder if her dark secret will be discovered. And what will happen to her if it is?