Well life isn't always that simple, many countries don't give you the luxury of just giving up a job and readily find another one, let alone that pays just as much or one at all for that matter.
Also she did mention she wanted to save money for her son future/education, so she probably did weight both outcomes and she'd rather be willing to go through a blowjob or even subsequent "dates" than all that stress and uncertainty that would come from losing the job and cause her to cry out in desperation.
Then again its her character choice, you can always influence it and possibly help her with the burden