She could have dementia

As a man over 60 I can feel aspects of my short term memory definitely dropping off. Not helped as I'm deaf and struggling to structure most sentences spoken to me from the fragments of the words I hear. I have hearing aids but only so effective.

I'd suggest if your mum is OK explaining it to a doctor, maybe having a memory test done to look for other things it might be. But high street places like boots or specsavers will do free hearing tests. Don't be pressured into buying their expensive hearing aids unless certain they'll help you. But should be able to rule out that.

When I had my first one 5 year or so ago. The "cocktail party" test was illuminating just how little I could determine.

I did not notice any change in my wife's memory, and she says she didn't think it got worse at that time. Both of us began to notice lapses in our late 60's, but nothing major.

No women answered this for you? Geesh.
It didn't affect mine during that time, no.