I'm 58 but I'm scolded like a child

There is a pervasive sadness that follows me these days. I am often worried about Mom's safety, but also fearful of a new side of her personality--she now scolds me more often than I was ever scolded as a child. Here is a perfect snapshot of one such encounter:
Mom needed a small order of groceries and would not meet the minimum requirements of Peapod. We located a small grocery store in her neighborhood that would accommodate her needs. She needed to establish an account with them for her credit card and she set out to do that while shopping there, with her male friend. She had also given me the shopping list before this outing.
When I found out that she was planning to go there herself, I was so proud of her ability to be independent again, that I threw away the list--thinking I wouldn't need it.

Well, that turned out to be a giant mistake! She went to the store with her friend, but only opened the credit account and bought NOTHING!!! Then she called and asked me to place the order. When I explained that I no longer had the list, I was shouted at and scolded as if I were 10 years old--in fact, she never yelled at me like this, when I WAS 10 YEARS OLD!

Herein lies the problem I face each day-- at one moment Mom is perfectly logical and reasonable. At other times, she is angry, beligerent and mean-spirited, telling me that I'm not helping enough or equal to the help her male friend receives from his family. Honestly, I'm not in competition with his family, but they're not helping more, he just needs less help!

I used to love calling to talk to my mother. Now I fear each phone encounter--for I walk into a landmine, not knowing which personality will be on the other end! This person embodied in my mother is not the same loving, rational woman I used to know, yet she is housed in my mother's body--I know this will only get worse with time, and yet Mom continues to insist that she is managing completely on her own and won't accept additional help. HELP!!!!