Desire By Design by Heather Boyd

A surprising offer…
Spinster Sylvia Hillcrest will never marry, but that does not mean she has to ignore the occasional flirtation aimed her way, or the chance to indulge her secret vice in societies best card rooms. When she’s suddenly given a fortune to wager, but asked to lose it to one particular family, it’s an intriguing challenge too irresistible to pass up. So too is the devilish marquess carelessly flirting with her every chance he gets.

…a secret delight
Faced with a situation he cannot solve alone, the Marquess of Wharton designs a masterful scheme to use Miss Hillcrest’s hidden talents for cards to pass a small fortune to a desperate friend. His plan, of course, was destined to succeed, and he spends one scandalous night celebrating with the spinster in his bed. They agreed it was just a fling, but what’s a marquess to do when he craves so much more?