Tracy, as well as what BB has posted, I would say the following - as you will probably already be aware, dementia is a ‘progressive’ illness (a bitterly ironic term - it is actually ‘regressive’ in its impact on the patient), and it will worsen inexorably. Eventually, unless ‘something else’ kills your aunt (eg, stroke, heart attack etc), the dementia WILL kill her.
By the time it does she will be in a dreadful state. She will be bedbound, unable to talk, doubly incontiendent and barely aware of her surroundings. This has just happened before Xmas to my poor MIL. It took less than five years to turn her from someone at 89 completely capable of living an independent life in her own home (400 miles away) to someone who could not even feed herself, etc etc.
I say this to point out to you that laudable as it is to want, very naturally, your aunt to remain as independent as she can for as long as she can, you are ‘fighting time’ …as in, whatever your efforts to slow down the dementia (and it can sometimes be ‘muted’ or ‘moderated’ perhaps) at some point, the above will happen.
so you do need, sadly, to ‘think ahead’ for when the grim time comes when she will need 24x7 care, and most likely this can only be provided in a nursing home (sadly, you know this already for your poor mum).
so whatever plans you make, they are only and can only be temporary, and long term planning is going to be needed from the off.
Any chance, by the way, whether your aunt could (when the time comes) be in the same nursing home as your mum? Would that work at all do you think? it would be nice if it could!