Beyond the Hunt by Mary Ann Weir

For too long, lunar witch Serafina Bell has been trapped in a cage of servitude to her cruel stepmother. But when she’s offered up in a marriage contract as part of a truce agreement, she seizes the chance to turn it into a key—one that might finally set her free.
To princes Casimir, Zane, and Koa Cimmerian, the assignment is simple: Uncover what their unwanted bride’s step-crone is plotting. In return for saying, “I do,” the dhampir half-brothers will gain an estate, a fat treasury, and, most importantly, their freedom from the vampire court. They expect an easy arrangement with a disposable bride.

What they get is Seri. Battered, bruised, and left for dead on their doorstep, she is nothing like they imagined. Especially when she opens her eyes… and the truth is revealed.