My 88-year-old Mom lives alone, can not drive, is in poor health, and has age-related dementia. She is not interested in AL and insists on remaining in her home. I live close by and have been her go-to person for several years now. She asks for my help or for me to visit her almost daily. I've tried to set healthy boundaries with her over the years and have been pretty successful. However, lately Mom is becoming more and more resentful of me not doing what she asks. At first she was very understanding and would say for me to help when I could. Now she makes sarcastic and sometimes childish remarks when I tell her "no", and frequently becomes angry. She doesn't do this to anyone else but me. She is sweet to everyone when I take her places and is very appreciative of anything someone else does for her, especially my siblings (who seldom even visit Mom). But, she told me the other day that I need to "step up" and do more for her. She even told me that she raised me poorly because of "bad attitude."
Does anyone have advice on how I should deal with this? I would love to explain to her that her snarkyness makes me want to do even less for her and with her.