The Last Faoii by Tahani Nelson
The faoii have protected Clearwall for generations. With militaristic order and stalwart discipline, these women have reigned in prosperity. But when her monastery is attacked and her sisters slaughtered, only young Kaiya-faoii is left alive.
Forced to cope without the long-standing traditions of her Order, Kaiya travels the country on a mission to avenge her sisters and preserve what is left of her heritage. The search brings her not only to dark discoveries and ancient family secrets, but to something she never wanted or dreamed of: a brother she never knew she had.
Forced into a war at the heart of a broken empire, the siblings must evaluate the true meanings of enemy, betrayal and freedom―and the gray areas surrounding each. Kaiya slowly learns the true state of the world outside her monastery’s walls, the dangers of the poisonous army that is slowly covering the land, and of her own innate abilities gifted by the Goddess.