Godsgrave by Jay Kristoff

Mia Corvere has found her place among the Blades of Our Lady of Blessed Murder, but many in the Red Church hierarchy think she's far from earned it. Plying her bloody trade in a backwater of the Republic, she's no closer to ending the men who destroyed her familia; in fact, she's told directly that Consul Scaeva is off limits. But after a deadly confrontation with an old enemy, Mia's suspicions about the Red Church's true motives begin to grow.