Clare K. R. Miller

When Noemi's father dies, leaving her an orphan, her unpleasant relatives don't waste any time before shipping her off to a poor, out-of-the-way boarding school. For Noemi, that turns out to be the best thing they could ever do for her—and the worst. She learns of the powerful magic at her command... and of the danger that threatens her, simply because of the star that guides her. Many people would like to control or destroy her, and she cannot tell who to trust.

Solitary Star is the first book in the A Star to Guide Her trilogy. If you wish to go on to books 2 and 3, they are titled Wandering Star and Pole Star.