Teenage Badass by Konstantine Paradias

Finn is a Helfwir, a monster hunter born. At the age of 8, Finn was perfectly capable of destroying a vampire with a plastic spoon. By the time he was 10, Finn knew a hundred ways of killing pretty much every thing that went bump in the night. Now, on her 14th birthday, Finn decides she wants to try living a normal life. She leaves home for Orsonville and enrolls in its high school. There, Finn will have to learn to deal with petty bullies, tenuous friendships , the hardships of teenage love and a werewolf cult that's hell-bent on world domination, all without revealing her true identity. This is shaping up to be a long, tough school year for Finn.