The Cry of the Icemark by Stuart Hill
When her father dies in battle, fourteen-year-old Thirrin becomes Queen of the Icemark, a tin kingdom forever caught between dangerous neighbours. But she bears a heavy burden. Thirrin must find a way to protect her people from the most terrible invasion that her nation has ever known - and do so before the end of the winter snows. "The Cry of the Icemark" is the glorious story of how she rallies her country and finds some extraordinary allies: Vampires, Wolf-folk and most noble of all, giant Snow Leopards. But it's also a heart-felt tale of duty and sacrifice, of unexpected laughter and awful uncertainty, and of a girl whose friendships are forged in the heat of battle.