The Boneless Mercies by April Genevieve Tucholke

Frey, Ovie, Juniper, and Runa are the Boneless Mercies—girls hired to kill quickly, quietly, and mercifully. But Frey is weary of the death trade and, having been raised on the heroic sagas of her people, dreams of a bigger life.
When she hears of an unstoppable monster ravaging a nearby town, Frey decides this is the Mercies' one chance out. The fame and fortune of bringing down such a beast would ensure a new future for all the Mercies. In fact, her actions may change the story arc of women everywhere.
Full of fierce girls, bloodlust, tenuous alliances, and unapologetic quests for glory, this elegantly spun tale challenges the power of storytelling—and who gets to be the storyteller. Perfect for fans of Maggie Stiefvater, V.E. Schwab, and Heidi Heilig.