These feathered flames
(Book)

"When twin heirs are born in Tourin, their fates are decided at a young age. While Izaveta remained at court to learn the skills she'd need as the future queen, Asya was taken away to train with her aunt, the mysterious Firebird, who ensured magic remained balanced in the realm. But before Asya's training is completed, the ancient power blooms inside her, which can mean only one thing: the queen is dead, and a new ruler must be crowned. As the princesses come to understand everything their roles entail, they'll discover who they can trust, who they can love; and who killed their mother"--