I sense you are looking for less of a should I stay or should I go answer. It seems like you are asking two different questions but you are only looking for a response to the obvious question. Obviously an adult is able to attain work and help out financially in a relationship. I will admit the second question is a lot more complex. Why can’t she just take “any job”?
I’m not an expert or anything but being someone who struggles with both focus and authority I get where your girlfriend is coming from. Working at an unsatisfactory job will just lead to resentment. The income she is bringing in will mean next to nothing to you personally while she is expected to stay unhappy for your personal gain. I’m not saying you shouldn’t expect her to contribute financially but just taking any job will not help either. Taking “any job” will lead to either her being let go or her quitting out of frustration.
Instead of expecting her to go out and get “any job” maybe ask her to start contributing a certain amount of dollars towards household expenses by a reasonable date. You would be surprised how much a little bit of communication can help in any relationship.
I highly recommend the commission sales industry. There is nothing more rewarding then making your own money.
Hope this helps!