Gabrielle Lane, Agent Blackhawk, is an agent with MI6.
She has been with the Firm for a decade. Getting accepted into the organization was, obviously, just the first step. The training would decide whether she would actually become an agent and from the beginning of that in an SAS training facility in Ireland, her chief instructor had "tried to break her; too pretty, he had said. What's a girl like you want to be here for? Give it up and go back to shopping". Hardly the most encouraging approach but it sealed her determination. "On the last day she had gone in to his office and delivered a sharp blow to his testicles. She wasn't going to be forgotten quickly".
Lane's work is not just intelligence gathering but also problem elimination (my word but I think she would agree). When directed, she has shown no qualms about taking out those deemed enemies to the state and she is very flexible when it comes to how. She had been extensively trained in hand-to-hand combat and "is comfortable with knives, guns and hands as her weapons. She favours operations where she is the killer, it is neater. Involving other people in an op always makes it difficult but she accepts that it happens. Working solo in operations over the last ten years has given her a lone wolf mentality; 'trust no one' is one of the truths of MI6. You never know who is reliable, or has been turned as a double agent, or has just lost it".
We are never given that much of a description of Lane. We learn that she has dark hair, is extremely athletic, and that she is quite thin. As mentioned above, she is very attractive which has helped her get close to a few valued targets from whom to extract intel or to dispatch or both. Her age is likely to be around 35. She is undoubtedly a native-quality speaker of German since she has been stationed in Berlin for several years and almost considers it home.
One interesting aspect to her personality comes from a fellow agent and one of the few she has let close to her. That man said of Lane comparing the city they were in to Lane herself, "Berlin looks sunny but slightly cold, not unlike your good self."