Amethyst: Princess of Gemworld - Shannon Hale - Bog

Amaya, princess of House Amethyst in Gemworld, is something of a troublemaker. She and her brother have great fun together until a magical prank goes much too far and her parents ground her to Earth! They hope a whole week in the mundane world will teach her that magic is a privilege and maybe washing dishes by hand will help her realise the palace servants should be respected.