No solutions. It is normal for someone with dementia to take a dip in hospital. Their orientation is so dependent on familiarity and routine.
That said in your position I would want reassurance that the stroke has not led to any brain damage or is associated with vascular dementia. Or that, in a warm hospital, perhaps not drinking as much as she normally does and surrounded by ill people, she has not picked up a UTI or similar.
My 88 year old mother, with dementia, was in hospital a few months ago following a fall caused by a UTI, and I pushed for an early discharge, albeit with hugely expensive 24 hour care, simply because I wanted her to retain as many independent living skills. But a stroke is different and more medical. If she is discharged though I would go for too much support in the early days rather than risk having too little and a repeat hospital admission.
I am facing similar problems in that my mother, happily settled in very sheltered accommodation and with a carer coming in daily, had bad hip pain. My fear too is that a medical problem and dementia may be the tipping point, which forces her down the care home route. The X ray is today, and my fingers are crossed as it is a decision I don't look forward to making.
I would start really asking round about different alternatives. Sheltered, care homes etc. All sorts of people will have knowledge/experience: vicars, plumbers, estate agents, and there is a great deal of variety in quality of provision.
I would also look at convalescent care to see if a break, where she is fully looked after and can have a rest, could help her back on her feet. Or options for care at home. It will be vital on discharge that she eats well.
Others will know better than me, but I would try to make early contact with the discharge people at the hospital to discuss options, and what forward planning can be done, like a physical assessment of her home by social services. Neither you nor the hospital will want her in hospital any longer than she needs to be.
Its grim isn't it.