Annabelle Perkins is an agent with the CIA.
I would also be quite accurate by saying that she is a thief.
She is both, though it is because she was so very good at the latter that the Agency wanted her to be the former. We learn in the opening paragraph of the first recorded adventure that when she "was a teenager, she was sentenced to juvenile hall for theft. Today, she works for the U.S. government." In the second paragraph, we learn that "once just a thief who stole for nothing more than to feed herself", she is now "one of the best stealth operatives in the world".
Her story takes place quite a few years in the future (the year is 2048 to be exact). There is a "highly classified black ops program known as the Specter Program. The CIA program finds and trains some of the best stealth operatives on the planet known as the Specters, soldiers who leave no trace or footprint behind. The purpose of Specters is to sneak into some of the most secure places on Earth to secure intel critical to national security."
Perkins is one of these Specters. She is described as being 28 years old, "standing at six foot one with pale white skin, a slim figure, and long, dark raven-black-colored hair from the parted center on the top of her head, coming all the way down to her shoulders". She is also said to be one of the best operatives in the Specter system. If you asked her, she would gladly admit that "nobody is better" than she and this high regard for her own abilities comes from several years proving she is the best there is.