Amethyst: Princess of Gemworld — Shannon Hale

Amaya, princess of House Amethyst in Gemworld, and her brother love magical pranks. But when one goes much too far, her parents ground the young royal…to Earth! They hope a week in the mundane world teaches her that magic is a privilege…and maybe washing dishes by hand will help her realize that the palace servants should be respected. Three years later, “Amy” has settled into middle school and ordinary life. She doesn't remember any other home. So when a prince of the realm brings her back to Gemworld and restores her magical destiny, how will she cope?