Jenny is the balancing force between her polar-opposite brothers. She very much has eyes for Billy Creel and he for her, which is why Billy comes to the restaurant to eat. Like her brothers, Jenny was born in Megaton in the days before the fence. She took over the restaurant with her brothers when her father died.
According to Colin Moriarty's files, Jenny Stahl was almost raped by, or had some kind of affair with Jericho. Despite having found this evidence, the player cannot ask Jenny about it. There is however an audio conversation between Jericho and Jenny about how it was a long time ago and how he, "knows what her problem is...". If you wait around you can hear Jericho trying his luck but is unsuccessful.