One of several siblings, Gabrielle was born to a family that couldn't quite afford to keep her and her siblings. Gabrielle is one of the older siblings, and tended to take on a lot of responsibility for her younger siblings and help keep them out of trouble. Her family were born in Pyxis, and in Pyxis remained throughout much of her childhood.
Eventually, though, their mother died and their father walked away from it all, and Gabrielle did what she could to keep the family going. Some of the means of making money she decided to turn to were somewhat questionable and dangerous, but it was whatever. One of her clients, though, discovered she had rather the brilliant mind, and the next thing she knew, he was talking about getting her into Erebos University. Unfortunately, none of the Brenners were registered.
Ultimately, and she isn't sure, even now, if it was that client that did it, or fate, or whatever, but one morning Suyis motherfucking Maitra was sitting on the stoop outside their house. He said he wanted to adopt them, and while Gabby was skeptical, he seemed genuine. Eventually, she agreed to at least meet the others he'd adopted and spend some time in the Pyxis Tower.
And they never did go back to the Grid.
Since then, Suyis did indeed adopt and register them all, and insisted Gabby go through school and eventually she graduated from Erebos University, having decided she wanted to be a doctor. Not just any doctor, a mental health doctor. The Republic, probably through influence of Suyis, Jadyka, and maybe Jahan, decided to hire her on to the Medical department, and she's been a psychiatrist for the Special Other Forces ever since.
She tries not to get too attached to her patients, but she does always wonder how they're faring when she isn't in contact with them. Most recently, she got a telepathic Losrian who had a twin brother the Republic wouldn't let him see. She got a decent way in getting him to open up to her, but, he was ultimately reassigned because she was taking too long.
It's the story of her life, really.