Mending Fate — Elisabeth Waters

Seventeen year-old shape-changer Zora lives at the isolated estate Eagle's Rest, where she has spent her entire life being trained to be the next priestess of the Earth Mother. But when the old priestess dies, the Goddess chooses her cousin Kassie instead, leaving Zora hurt, bewildered, and wondering what to do with the rest of her life. She takes Kassie's place on the annual search for more shape-changers for the school Lord Ranulf runs, and an additional errand at the end of the trip sends her and her cousin Kyril to a matriarchal city-state named Diadem. There both of them are chosen by the Goddess, for very different roles, and Zora learns that much of what she knew about herself and her parents wasn't quite the truth...