The Submissive Bodyguard

Brooke is just out of the army when she runs into Jacob, who works for a high-level security company. He convinces her to join their company, where her martial arts and familiarity with weapons will make her a rare thing - a female bodyguard. Jacob had, in the process of convincing her, taught her just how wicked and exciting bondage was. She found his power exchange games incredibly thrilling despite her lifelong determination that everyone treat her with respect and dignity.
And on her first assignment, with a famous and wealthy singer named Kaylie Moore, she found Moore doing the same. Kaylie lives alone in an enormous mansion, but with constant security. The guards all stay outside. Except for Brooke, who Kaylie quickly seduces and begins a scalding game of mistress and slavegirl. Brooke isn't gay, but she can't resist the woman's charms and skills and is soon writhing in pleasure.
And then Kaylie makes an offer she can't refuse. She will triple Brooke's salary to be her personal, live-in bodyguard and slave girl. Of course, that will involve rather different training than the security company gave her. But for that kind of money, Brooke will learn do as she's told, dress how she's dressed (or not), and learn to protect, as well as please her new boss in every way Kaylie wants - or be punished.