I Love the Earl (The Truth About the Duke)

A single lady in possession of a good fortune must be in want of a suitor
Margaret de Lacey has accepted her unmarried state with dignity, if not delight. She had no suitors when she was young and starry-eyed, though regrettably poor, and it's unlikely any man will court her now that she's older, wiser, and still just as penniless. Until, that is, her brother unexpectedly inherits the dukedom of Durham and settles an enormous dowry on her, making her the most eligible heiress in town.
No gentleman in London is more in need of a wealthy bride than Rhys Corwen, Earl of Dowling. He contrives an introduction to Margaret because of her dowry, but she swiftly sets him right: no fortune hunter will win her heart or her hand. Far from put off, Rhys is intrigued. Interested. Entranced. And soon the only thing he needs more than Margaret's fortune . . . is her love.