Child Of The Prophecy by Juliet Marillier

In a world where ancient magic and prophecy intertwine, a young girl named Fainne is thrust into a destiny she never sought. Raised in isolation by her sorcerer father, she is sent on a perilous mission to destroy the Sevenwaters family, whose fate is crucial to the balance of power between the human and fairy realms. Torn between her loyalty to her father and the bonds she forms with the people of Sevenwaters, Fainne must navigate a treacherous path of deception, love, and self-discovery. As the final piece in a generational saga, her choices will determine the future of her world.