The Veiled Empress:

Aimée du Buc de Rivéry was a French heiress who went missing at sea as a young woman. There is an unsubstantiated legend that she was captured by Barbary pirates, sold as a harem concubine, and was the same person as Naksidil Sultan, a Valide Sultan (Queen Mother) of the Ottoman Empire. The strangely romantic story—heretofore a baffling mystery—of the lovely French girl who became Crown of the Veiled Heads reveals an unknown chapter of history and throws a new light upon the revolution in Turkey