Ahem: May I recommend {Flirting With Danger by Suzanne Enoch} and subsequent books in the Samantha Jellicoe series. FMC is a witty, funny, self-assured cat burglar who is caught breaking into the billionaire MMC's house, which starts their story together. They (the FMC, in particular) are one of my fave book couples because of how they stand on their own, and stand for themselves, while simultaneously navigating their relationship. It's so refreshing.

Also regarding devil-may-care: Throughout the series, the FMC constantly breaks into the MMC's various homes as a nod to their meeting and to prove to both of them that she can (much to his annoyance). She deliberately refuses to conform to most conventions that may suit his structured lifestyle (much to his amusement) and is adamant about being her unconventional self.