The Dragon's Precious Princess

Princess Elena's three brothers fall under a curse after trespassing into dragon territory, and she offers herself as a sacrifice to save them. The dragon does not harm her, but instead treasures her in ways she never expected. When she finally returns home, she discovers her brothers have taken in a new princess named Lillian, who repeatedly pins false blame on Elena. The rivalry turns deadly when Lillian invents a curse that supposedly requires Elena's heart, and the brothers respond by once again choosing to sacrifice her.