Sister & Serpent — Gwyn R. Lyon

Princesses Sophia and Rosalinda grew up opposite each other in every way: Rosalinda is beautiful, but lacks intelligence and grace, while Sophia is witty and charming, but ugly. When Rosalinda's true love breaks the curse that keeps her idiotic, it seems that Sophie will be forever forgotten, unless she can change her luck herself, and break her own curse. But can anything be that simple?