Unearthly (Unearthly, 1) / Cynthia Hand,

When Clara Gardner learns she’s part angel, her entire life changes. She now has a purpose, a specific task she was put on this earth to accomplish, except she doesn’t know what it is. Her visions of a raging forest fire and a mysterious boy lead her to a new high school in a new town but provide no clear instruction. As Clara tries to find her way in a world she no longer understands, she encounters unseen dangers and choices she never thought she’d have to make—between the boy in her vision and the boy in her life, between honesty and deceit, love and duty, good and evil. . . . When the fire from her vision finally ignites, will Clara be ready to face her destiny?