Job hours question???

I like my job a lot, although it only pays min wage, but my boss never can seem to keep her promise on set hrs. by that, i mean for a couple of wks i get my full time hrs and the next part time. when i was hired she told me 35 to 40 hrs. I never know what hrs I will get she only schedules a week at a time. I believe this on deliberate, so as to keep not just me , but my coworkers in the dark regarding our hrs. I get the swing shift aspect but, I really need hrs I can depend on so I can arrange making bill payments. I have two questions. Is there a way to get her to set me with more dependable hrs, without offending her, or should I apply elsewhere, for a job that will help suit my needs better? I really need full time hrs. Any advice and opinions are welcome.