Second Choice. Golden Child.

Cecily and her sister are sent to court to bear dragonlings for the Crimson bloodline. In her past life, Cecily married Prince Tristan but birthed only a lowly black dragonling and was killed. Reborn, Tristan chooses her sister instead. Cecily marries an Ancient Gold Dragon, bears a gold dragonling, and finds happiness while Tristan's true serpent nature is exposed and destroyed.