I do feel for you Chris. I think - hope - your Mum will get over it in a bit. For now she is recoiling from being told off and, in fact, being found out for saying things she should not have. Sulking like a recalcitrant teenager. I agree with your reaction in not taking any notice. Just don't feed the situation. If she wants to get her own shopping that's fine, but probably just don't comment on it. Your Mum is lucky to be looked after by you and I'm sure she won't keep this up for long. Your sister was right to speak to her though. Good luck!