BTW - my wife has from time to time said "i'm not your mother" when referring to the housework etc. I find it insulting and have said so. She said the very same thing at the MC the other day saying "I feel like I'm his mother sometimes".
Usually when the wife makes that statement it has to do with her feeling as if she is having to take care of him as though he is another kid. It may be picking up his clothes, cleaning up his messes, choosing which clothes he wears, making sure he takes his medicine, reminding him of appointments, telling him how to do things, etc.
To be fair, a lot of women lump the H in with their kids and treat him as though he were another child, instead of a grown man. She will talk down to him as if he were a child. She'll give him orders or instructions. She has no problem in telling him not to do or say something. She corrects him, even in front of the kids. She'll put food on his plate. Tell him he shouldn't eat certain things and try to take it away from him. Lay his underwear or personal things out every day. Help him get dressed, pack his bag, etc. Things that he is fully capable of doing, but she either feels he won't do it correctly or it makes her feel better in some way. However, if it causes resentment....it needs to stop immediately.
If I were in your shoes, I think I would make sure I did not leave a trail of clothes, shoes, food, papers, empty pop cans, coffee cups, trash, or personal items. Don't ask her where something is (just b/c that's the easiest and quickest way), when you can look for it. For example, "Honey, have you seen my house shoes"? And they are in the same place as they have always been kept. "Is there any ice cream in the freezer"? Go look for yourself. Clean up after yourself. Don't ask her to take something to you, if you are not disabled. If you bring things in from the store, put the items away yourself.
It sounds to me as if she's just complaining about having to do housework. Well, so what? Most women have to do housework. If you were not there, she'd still have to do housework. She needs to either get over it, or hire a person to come in once a week and clean. Where I live, you can find someone to do it pretty reasonably priced, and it might be worth paying if it would take care of the problem. Frankly, I think she's just using that for her excuse b/c she doesn't have anything legitimate, and she knows it.
As for how to respond when she makes the crack about not being your mother, I understand what you are saying, but I really think she's complaining instead of trying to openly disrespect you. However, I can't see her face or hear her tone of voice, so I could be wrong. If you feel disrespected, then it's a strong possibility that's what she's doing. Have you ever point blank asked her what you can do to stop her from feeling like your mother? Or have you asked exactly how she means she feels like your mother?
I think your explanation about the housework was excellent. Apparently, she never thought about the fact you had a fulltime job and that she hers should be keeping the home. Was she spoiled by her parents? I mean, was she never made to do any type of work, especially for another person?
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!