Our lady of pain - M. C. Beaton

Lady Rose Summer prides herself on not being a jealous woman - and she knows her engagement to Captain Harry Cathcart is only a ruse to keep her parents from shipping her off to India to find a husband. But then Harry's latest client, Dolores Duval - French, curvaceous, flirtatious - starts appearing everywhere at his side. And that changes everything.

In a fit of temper Rose threatens Dolores - only to be found the very next day standing over her dead body. Only Harry can clear Rose's name - and to do that he has to put the real murderer behind bars...