Seducing Cinderella (A Fighting for Love Novel) by Gina L. Maxwell

Mixed martial arts fighter Reid Andrews's chance to reclaim his title as light heavyweight champ is shattered when he's injured only months before the rematch. To make sure he's healed in time, his trainer sends him to recuperate under a professional's care—Reid's best friend's little sister, all grown up. Disorganized and bookish Lucie Miller needs some professional help of her own. She'd do anything to catch the eye of a doctor she's crushed on for years, so when Reid offers seduction lessons in exchange for 24/7 conditioning for the biggest fight of his career, Lucie jumps at the chance. Soon Reid finds himself in the fight of his life...winning Lucie's heart before she gives it to someone else.