Willow's Power

Eight year old Willow becomes terribly sick and magically heals herself using a newly discovered power. After meeting her brtoher, Louis, who she didn't know existed, she learns that her parents are not who she thinks they are; she had been kidnapped at a young age. Her brother takes her to go meet her real parents, but they run into some trouble on the way.

(p.s. I started this book when I was like nine so it sucks for like the first twelve or so chapters)