My Lady Rake by Ari Thatcher

Verity Stanhope loved well until her husband’s death. She has no need for love now, in her thirties, but she’s never lonely, thanks to the young men who are more than happy to learn the lessons in seduction she’s said to offer. Then she meets temptation: Oliver Fitzallen, Earl of St. Ervin. He’s not looking for an affair, a mistress, or a night of bliss. He wants her heart and will settle for nothing less.