Delicate Hearts. Hibiscus Hearts series, #5

Quinn Bateman never thought her marriage would end so epically, but finding her husband in bed with another woman will do that. Starting over in Hawaii is exactly what she needs. Kai Olsen has always been the fun-loving playboy, never interested in settling down. But when he befriends a mysterious stranger, he finds himself drawn to her like never before. As Quinn and Kai grow closer, their friendship blossoms into something more than either of them expected.
But Quinn can't outrun her past forever. And when it shows up on her doorstep, threatening to ruin everything, Quinn knows she will do anything to protect her delicate heart.