The Spy by Nana Malone

Okay look, we all deserve one great nemesis in this world, maybe two. Hell, my sister stays in my top spot. But is it too much to ask that my best friend’s big brother, NOT be one of them?
Bonus points, he’s also my boss.
The Rogues Division is a top-secret, highly-classified, “I’d tell you but I’d have to kill you” kind of organization. The kind of organization the government pretends not to love having at its disposal. And Gabe Webb sits at the top of this badassery mountain.
I’ve finally gotten control-freak, too serious Gabe to respect me after six long years of his scowling and brooding at me with the occasional growl thrown in.
But when I get assigned a deep cover operation as a billionaire asset’s pretend girlfriend, suddenly Gabe doesn’t trust me to manage the assignment on my own and goes so far as to assign himself as my handler.