Job: S.H.I.E.L.D. Agent
Personality: For the most part Jess does not like people. She's taken a liking to Tony Stark because he saved her and was there when she woke up from her coma but other than that she's a loner. If missions require her to work with others then she shuts up and follows orders without question to keep herself out of trouble.
Back Story: Jess grew up poor, and that meant she had plenty of time and opportunity to hone a lot of skills that came in handy for keeping herself afloat. Mostly stealing and pick-pocketing and things of that nature, though of course she got caught plenty of times and spent her fair share of months in juvenile facilities and then actual jail as she got older.
When Loki attacked and the Avengers assembled, Jess was in the crowd. She stood up to the mad god, giving him a piece of her mind and refusing to kneel before him. So Loki killed her, though her death only lasted a few minutes before she was rescued. Tony Stark decided that since she had shown such bravery to stand up to Loki he would save her if he could, and she was kept on ice until Loki was dealt with. Once that whole event was over Tony went to work bringing Jess back, though the only thing he could not fix was her heart. After two rejected transplants he decided to use his technology to build her one instead, and once her incision had started to heal Jess was woken from the coma. Her first sight was Tony standing over her, explaining everything gently.
Awake and alive, Jess was offered a position within S.H.I.E.L.D. not only for a stable job but so that Tony could keep an eye on her and make sure her heart didn't fail. Jess agreed, and she's been with the agency ever since. She gets regular checkups from Tony but other than that hasn't seen fit to make any friends, though she also doesn't seem to mind the solitude of it all and is just living her life one day at a time for now.
(Avatar image made with Subeta's on site wardrobe function and copyright Subeta. Character is mine, everything else copyright the creators of Marvel Cinematic Universe.)