Eva Driscoll is an agent with the CIA.
That is very important to her back-story as it shows clearly how well trained she is and just how effective she can be in a 'situation' but her involvement with the Agency from the start of the first recorded adventure is quite limited because from the moment we meet her, she is setting things up to be a rogue agent.
As a child she had been extremely close yet very competitive with her brother Jeff and when he opted for the military rather than college, she took the same route a couple months later. Still having fun trying to best each other though they were not stationed together, Driscoll was pleased to have gotten her first stripe just before him and was eager to keep the vying going. Then Jeff one-up'ed her by going into the Special Forces which at the time were off limits to females. She felt there was no way to ever top that in the military so she made a huge switch and joined the CIA.
As she put it, "they took one look at my school and military records and offered me a role in clandestine services". That gave her an opportunity to really push herself but the secretive nature of her work prevented her from telling anyone what she really did, including Jeff, so as far as he knew, she worked for the DMV. For the next few years, her work would keep getting more dangerous and she would continue to prove just how good she could be.
She would still be doing it if someone hadn't killed her brother. At that moment, nothing was more important than finding out who was behind the deaths of him and two others soldiers with whom he served.
Driscoll is described as "stunningly beautiful, but not in a conventional way. She had the slightest of overbites and her top lip rose at the center. Her nose also seemed a little pointed, but her imperfections somehow came together to create the most captivating face [he] had ever seen." To one man who would become an intricate part of her world, her most compelling feature was her eyes. "He'd never seen eyes like hers. They looked like emeralds, the brightest green he'd ever seen, and the shape hinted at Asian ancestry."
As alluring as she is in appearance, to those fighting alongside her and more so to those going up against her, Driscoll's highly competitive nature and her incredible skill set makes her one tremendous fighting machine. Considering the powers that she is combating, she will need to be.