Not Quite a Lady — Sara McCulloch

She was not his first love, but she would be his last.
Angel was a beautiful, silver-eyed waif; a seventeen year old girl whose gamine graces charmed London society. But now she was the ward of Matthew Vail, the dashing hero of the French campaign, he had impulsively rescued her from the evil intentions of his black-hearted cousin Martin--but what was he to do with a seventeen-year-old girl to look after?
For her part, Angel adored Matt. But to win him she had to seduce him from the worship of his long dead sweetheart and his very live mistress.