The Thirteenth Child by Erin A. Craig
Hazel Trépas has always known she wasn’t like the rest of her siblings. A thirteenth child, promised away to one of the gods, she spends her childhood waiting for her godfather—Merrick, the Dreaded End—to arrive. When he does, he lays out exactly how he’s planned Hazel’s future. She will become a great healer, known throughout the kingdom for her precision and skill. To aid her endeavors, Merrick blesses Hazel with a gift, the ability to instantly deduce the exact cure needed to treat the sick. But all gifts come with a price. - Baker & Taylor