Shade & Sorceress: The Last Days of Tian Di, Book 1 — Catherine Egan

Eliza knows for certain what she isn't: the powerful sorceress the learned Mancers think her to be. Or is she? Eliza is stunned to learn her father has been keeping important secrets. Her mother's death wasn't from pneumonia, but the death of all great Shang Sorceresses: killed in battle against evil forces. Even so, Eliza's lessons with the Mancers at their citadel show them what she has always known -- she can't do any magic. Imprisoned in the Arctic by Eliza's mother's final brave act, the evil Xia Sorceress uses her minions to capture Eliza's father. Escaping the citadel with her best friend Nell and new friend Charlie, Eliza sets off to rescue him. They seek help from the Triumvirate, an uneasy alliance of ultimate power -- the Oracle, the King of the Faeries and Swarn, the witch who delivered Eliza as a baby. They try to stop her, but she is determined. She knows she's connected to the Xia Sorceress somehow. What awaits Eliza in the Arctic prison is more horrible than she could have imagined. Abandoned by the Mancers and the Triumvirate, she must rely on her friends and her own wits and common sense to succeed in her quest.