Michelle Reagan is an agent with the CIA.
She is a NOC, or non-official cover, a simple way of saying she is on her own if things go pear-shape. 'Official' agents, working under the cover of an embassy gig with diplomatic privileges and some immunity, might have some promise of a rescue or a trade should local governments catch them in the act. No such luck for the NOC's.
In the case of young Reagan, she would fare even worse since her job is that of assassin. As she points out, "Officially, the U.S. government doesn't engage in assassinations. Officially. Even if the CIA doesn't acknowledge it, every Director has had a team like ours at his disposal. We're his option of last resort."
Reagan was just a year out of high school, 19 years old, wondering what she would do with her life when she received an offer to join the Agency. How and why she got that invitation makes up a section of the first recorded adventure so no spoilers here. But now she is a trained operative, albeit the youngest in the small cadre of wet-work specialists working under the control of the Directorate of Operations in the group known as the Special Activities Division, or SAD as she points out.