The mask and the crown-book 1: the mask

A young thief has made a desicion that will change her life. She has chosen to become a guardian. When she steals from the fire guardian, she is hunted down, but in order to escape, she must use her powers. So when they find her, she has a choice. Die, or become one of them. To complete the training, she must go to training school, where she will meet the Prince. He stirs a memory inside her long forgotten, and they instantly despise one another, but only together can they defeat the citizens of darkness. That's not what the prophecy says, but then again, it says the thief's soul must remain unbroken...