The Secret of Darkwood Castle — Heather Ostler

18-year-old Julia Levesque is returning to Lockham Castle for her third and final year of shapeshifting school. She's become a powerful werecat, completely embraced her siren side, and has found true love; but her problems are far from over. Julia is the lead candidate to become ambassador of Ossai, her world, in the hopes of ending the reign of the evil Guild. With her estranged mother as the Guild's dictator, she knows it won't be easy. She'll have to travel to Darkwood Castle, a sinister and hopeless palace in order to stop her mother from destroying Ossai. Julia must find a way to save her world-and those she loves most. Otherwise, they'll both be lost forever.