Echo of the Evercry - E. J. Dawson - Bog

The cost of magic has never been clearer.
Larissa's inability to kill is a disgrace to her absent mother, Sword Matriarch of the Fair Lady's order, a sisterhood whose purpose is to hunt down sorcerers corrupted by the Evercry and slay them. But Larissa hides an even more sinful secret: she is drawn toward magic, and it grows stronger in her every day.
Larissa keeps a stranglehold on her gift until the day of her graduation test, when her misuse of magic leads her to failure. Prepared to be cast out of the sisterhood, she is instead brought into the scorned caste of the darkkins, those who study and wield magic in the fight against the Evercry. In their halls she discovers that her proclivity for magic makes her powerful, and a little dangerous.
Gone for years, her mother suddenly sends word that she needs help to defeat a formidable sorcerer, help only Larissa can give. Larissa will do anything to save her mother, even travel with the girl who bullied her all through school. But as they battle monsters and mercenaries, Larissa must grapple with dark truths about the sisterhood and her heritage, and decide who she can really trust with her mother's fate...and her own.