Good vs Evil Fantasy Tale

I enjoyed reading this good vs. evil fantasy tale. It’s a well constructed fantasy with good guys and bad guys, clearly identified, and lots of imaginative world building. The main character, a teenage girl, is just discovering that she has unusual magical powers, and also that there seem to be a lot of people out to get her. It’s a good thing she’s got a “watcher,” a friend and companion, as she uncovers evidence that her destiny involves rescuing others.