Chappilass, I'm going a bit left-field to the rest of this discussion and asked if your Mum has had her urine tested for a UTI or the like? Alternatively, is she dehydrated? So many folks; young and not so young, don't drink enough.
A while ago my OH was complaining of vague moments, occasional lightheartedness and generally feeling wiped out. He had an extensive check out and all that was suggested at the end of it was to up his fluids. A man transformed.
He didn't have any of the classic signs of dehydration - pinch the skin sort of thing, but it seems his body just needed a bit more fluid than he was taking in.
On the UTI front, it's fairly common for this to make the individual feel pretty lousy, and in the elderly, it can cause terrible mental upset and confusion. In older folks, the confusion if sometimes the first sign.
Just a thought.