The Cheeky Minx by Merry Farmer

Every good girl deserves a very bad boy…
After one little moral slip, Miss Josephine Hodges was banished to Miss Dobson’s Finishing School to mend her ways. What could have been a misery has turned into a blessing in disguise as she helps her friends investigate the theft of a priceless diamond. But when Jo’s mother arrives at the school to inform her she’s been promised in marriage to none other than that notorious Lord Lichfield, Jo is in shock. How could she possibly marry the man she suspects of stealing the diamond?
Lord Felix Lichfield is desperate for a wife after rumors of his wickedness cause his fiancé to call off the engagement, but he never suspected his mother would stoop so low as to find a bride for him without his involvement. But when he meets the feisty Miss Hodges, things begin to look up. Except that he suspects his new fiancée has heard all about his reputation and wishes embrace it just when he would do anything to put that part of his life behind him.
There is more going on than meets the eye, though, and when Jo and Felix team up to hunt the diamond thief—and to explore their passions while they’re at it—anything could happen.