Enchanted Kingdom by Tricia Wentworth

Some women in Wylan had dreamt of this day. Some pined and planned for it their entire lives. Chosen for the Assemblages of Consorts, Jorah Demir will have the opportunity to vie for the twin crown princes’ affections. Though no one knows which prince will eventually rule, they are two of the most powerful Enchanted in all the kingdom. Not only is a chance for a crown at stake, but also a small drop of the royal bloodline's magic. Jorah isn’t interested in either. Both princes are Enchanted, the very type of people responsible for her father’s murder. From the lowest level of the kingdom and without magic, she is forced to go above the walls of Wylan and into the castle itself. She only has one goal: to avoid the crown princes and not, under any circumstances, form an attachment with either one of them. Surrounded by Enchanted at every turn, she soon learns not all are as evil as she assumed. And when the king's magic doesn’t affect her, everything Jorah thought she knew is called into question.