A Tapestry of Fire - Margaret Ball - Bog

Thalia Kostis is a budding magician (depending on how you define it), but she has a theoretical mathematician's grasp on socialization and people skills. When pressed into spying on a rival magician's company retreat to find out where kidnapped coders are being held, she expected things to go completely sideways. She didn't expect to end up mistaken for her rival's fiancée ... Now she has to juggle her own impending wedding, her cover, her magic, and company politics that might turn out deadlier than anyone expected!