"If my girlfriend did not work" is a shorthand for something else. I think it's shorthand for "sit around being lazy all day", which is an emotional decision and not the overt economical one. If your girlfriend is going to school full-time, then that's not work. Would you expect her to put in up to 20 hours of chores and meals on top of her studies? I don't think so.
Ahh, but perhaps you also meant to include potentially income-generating work (like studies) along with income-generating work?
Which then means that if your girlfriend gets disability pay then she doesn't have to do as many chores, right? Since even if she watches the TV all day she's still bringing in some money, as a consequence of work she's already done. (This can be extended to living off of a trust fund, or off royalty income.)
If you had children then would she also need to spend 100% of her time raising the children, on top of the chores? At what point do you start helping? Can you assign a monetary value on that?
Or, if you were making $1 million per year, then would you still request that she do all of the chores and meals? Because then it feels petty, when you could easily hire others to do it instead, and she can pursue her life's dream of developing free online education courses.
In the modern context, the delegation of chores is based on a combination of factors, including available time, interest in doing so, and tolerance of what happens when it isn't done. If you don't like it and can't deal with it, then you break up. In the modern context, breaking up or even getting a divorce is a simple task with little social stigma. Hence you have very little power over your girlfriend. If you "ask her to take care of all the chores and meals" then she can say "no", and leave.
100 years ago there was a much higher power imbalance. The woman couldn't easily say "no" and leave, even if the demands of the man were unreasonable, because it was much harder for her to have a normal life post-separation than for him.
In any case, simply saying "if my girlfriend did not work" is belittling because it assumes that work is the only thing that's important in a relationship, and it's secondarily gender biased because men tend to have higher incomes than women.