The Thirteenth Princess ( book ) by Diane Zahler

Zita is not an ordinary servant girl—she's the thirteenth daughter of a king who wanted only sons. When she was born, Zita's father banished her to the servants' quarters to work in the kitchens, where she can only communicate with her royal sisters in secret. Then, after Zita's twelfth birthday, the princesses all fall mysteriously ill. The only clue is their strangely worn and tattered shoes. - softcover - fantasy - perfect for ages 8-12 - great condition! - no ripped pages or stains