Heiress in Red Silk by Madeline Hunter

In one life-changing windfall, Rosamund Jameson goes from struggling shopkeeper to heiress—and co-owner of a new business. Not only will her sudden fortune allow her to move her millinery shop to fashionable London, but Rosamund will be able to provide her younger sister with a proper entry into society. The only hitch for resourceful Rosamund is her arrogant, infuriatingly handsome business partner…

Kevin Radnor is shocked that his late uncle, the Duke of Hollinburgh, bequeathed half his company to a total stranger—worse, a beguiling beauty who can only hinder his enterprise. But Rosamund insists on an active, equal partnership, so Kevin embarks on a plan: a seduction that will lead to a marriage of convenience, giving Rosamund the social status she needs, and guaranteeing him the silent partner he desires. Yet as this charismatic gentleman sets his flirtation in motion, he begins to wonder who is seducing whom—and if he can learn to share himself body and mind, without losing his heart . . .