We already knew that Jack had, for some reason, decided to supplement her generous fire service income by working in a bar (where she used to wear massively high stilettos all night, no?). Apparently Old Chief had no problems scheduling her shifts around a second job, but not her childcare.
It may be worth noting that she has previously claimed to have been driven out of several jobs by her (first) stalker, who would turn up to her workplaces to intimidate her. We also know that he was still stalking her when she was in the fire service...
Odd that she stayed in this bar job during those years then, isn't it?