The Scoundrel's Daughter (The Brides of Bellaire Gardens) by Anne Gracie

When Lady Charlton is forced into becoming London's most reluctant matchmaker, sparks fly and romance ensues, from the national bestselling author of Marry in Scarlet.

Alice, Lady Charlton, newly-widowed and eager to embrace a life free of her domineering husband  is devastated when a scoundrel appears, brandishing letters that could ruin her. To prevent their publication he wants Alice to find a noble husband—a lord!—for his daughter, Lucy.

Alice is forced to agree to his blackmail but when Lucy arrives, she has absolutely no interest in her father's scheme. A lord, she says, will only look down his nose at her—and she's having none of that!

Desperate to retrieve the letters, Alice enlists the aid of her handsome young nephew, Gerald, who in turn seeks the help of his former commanding officer, James, Lord Tarrant. James is soon beguiled by the marriage-averse lady and sets out to teach her about love.  Meanwhile, Gerald and Lucy strike sparks each time they meet.

To combat the dastardly plot, Alice and Lucy must learn to trust each other. But can Alice put the past behind her and open her heart to love?