Plenty of knowledge, advice and experience on this thread . . . but as Pawsy Bear hinted at, it’s important to find out what’s going on with this particular lady.
A few years ago, my own mum was so weak that she needed a wheelchair to attend hospital appointments. A few months later (after major surgery) she was climbing hills in the Lake District.
So it could be this general “decline” that TJ describes, or it could be a specific health problem (either physical or mental).
Either way, it’s extremely worrying to watch this happening to a parent. So I hope Pigface is able to get appropriate help for his mum very soon.