Memory Thieves by Bill Terry

When Princess Cammerrina (Cami) awakens on board a ship, she has no memory of anything in her life. In the process of trying to stay alive, she stumbles upon an insidious plan to invade her homeland and enslave the people. As her memory returns, so do her magical powers, and with the most unlikely allies, she sets out to thwart the effort of a demented wizard to steal ancient magic that could make everything she feared come to pass.