Jessica was born lucky. Her mother had been just another drug addicted whore, dependent on any man who showed her any kind of affection. Her father, had been a random john, a man her mother fucked for a little bit of money to support her habit. But the people who spawned him, aren't very important in the long run. She was lucky enough that her mother raised her until she was old enough to run the streets of London, and than one day the woman vanished. She either ran away, or was killed, but it turned out to be a lucky break for Jessica, because the son of a bitch who was sleeping with her, had been staring at her a little too intently recently, and with her mother gone, she had managed to dodge a bullet, and a lifetime of forced child prostitution. Understandably mistrustful of the system, the police, and anything resembling the law, Jessica promptly, and completely disappeared into the streets that she knew so well.
Again she was lucky, because although she hadn't started off as the most street savvy of kids, she was a quick learner, able to go long periods without eating, and had a willingness to do anything to survive. She even managed to find a group of other homeless kids to run with, and she learned the true meaning of safety in numbers. The six years she lived on the streets taught her many things, from picking pockets, scamming strangers, to how to slip a condom on a John who was unwilling to suit up. And the streets weren't just a home and teacher for her, it also gave a strange meaning to her life, and forced her to create her own boundaries, rules, even an odd sort of structure. So even though she was a criminal, he held to a moral high ground, that even upstanding members of society would find hard to follow.
When she was 14, she was incredibly stupid, and when she found a slightly open window, and compared it to her almost painfully empty belly, she took a risk, and added breaking and entering to her long list of felonies. It seemed a bit too good to be true at first, but even when the window creaked, and slipped inside, nobody came out to catch her in the act. So she got comfortable, eating what food she could find. And than she got curious, thinking that such a large and obviously expensive house must hold untold riches, so she started upstairs to look around. It wasn't until she heard a slight click when she tried to open a door, that she realized that she had made a big mistake. Moving quickly, she managed to dodge a trap, and than another, before she tripped over her own feet and took a tumble down the stairs.
When she woke up, she found himself in a strangers bed, almost completely naked, except for her raggedy pair of panties, and a sheet covering her body. It only took her a moment to realize that there were no other clothes, and that she was quite firmly trapped in a strangers room. She took comfort in the knowledge that she wasn't in jail, but she wasn't stupid, and knew that she could have possibly landed herself in an altogether more dangerous situation.
Again, the luck that had kept her alive for so long, had kicked in again, and instead of finding herself in the clutches of some child molester, she lucked out, and caught the interest of a rather 'eccentric' multi-millionaire. The man was older, already had a son around the same age as Jessica, but he saw something in the girl, and took his own risk by taking a chance on the little raggedy street urchin. It was the girls natural instincts, the way she anticipated an attack, and her quick mind, mixed in with her unbelievable luck, that in the end, made Jessica an apt pupil. When she was adopted, Jessica finally got a taste of a real home, and a real family. And so she was trained, and in the end took up the mantle of a first classed thief.
She spent decades doing what she loved, and she did love it. When she started getting older, she decided that she was ready to do something else with her life. Which, through a twist of fate, led to her contracting with the FBI, in return they'd erase her file from the database, and give her a comfortable salary. Art theft, was far from happy about this though, so she held little doubt that they somehow kept a record of her somewhere, in the deepest darkest depths of their file cabinets. And it was almost ironic, that her work with the FBI lead to her garnering more enemies, than she had throughout her entire criminal career. Even through all that, she kept to her code, and refused to give out actual names and intimate details of her contacts, instead guiding the various teams she's worked with in the right direction.