Learn to cook and help her with meals. In fact, I did just that - um - 55 years ago. When I married, my wife was super happy that I could do the cooking while she worked nights.
being a bad cook won't ever make people sick unless she is adding poison. A careless cook, on the other hand can indeed make people sick. Cross contamination, not cooking to proper temperatures does NOT effect flavor at all but surely can make people sick.
I would do what I have done since I was 12 and cook my own food.
I did have a mother and older sibling to teach me to cook but you have YouTube now that is likely to have directions to make almost anything.
My grandfather was said to be a bad cook so he went to cooking school and learned to cook bad tasting food nobody could pronounce.
I'd tell her that she can either learn how to cook the right way, or expect to never see you eat her food again. Tell her that she is in need of a major reality check in her life, and that if she ever tried to prepare that food for a professional chef, that she would be in for a real rude awakening.