The Ruthless Lady's Guide to Wizardry - C. M. Waggoner - Bog

A Tor.com Reviewers'' Choice Best Book of the Year
Sparks fly in this enchanting fantasy novel from the author of Unnatural Magic when a down-and-out fire witch and a young gentlewoman join forces against a deadly conspiracy.

Dellaria Wells, petty con artist, occasional thief, and partly educated fire witch, is behind on her rent in the city of Leiscourt—again. Then she sees the “wanted” sign, seeking Female Persons, of Martial or Magical ability, to guard a Lady of some Importance, prior to the celebration of her Marriage. Delly fast-talks her way into the job and joins a team of highly peculiar women tasked with protecting their wealthy charge from unknown assassins.
 
Delly quickly sets her sights on one of her companions, the confident and well-bred Winn Cynallum. The job looks like nothing but romance and easy money until things take a deadly (and undead) turn. With the help of a bird-loving necromancer, a shapeshifting schoolgirl, and an ill-tempered reanimated mouse named Buttons, Delly and Winn are determined to get the best of an adversary who wields a twisted magic and has friends in the highest of places.