My mother has started this. She's in assisted living but had a UTI not long ago and it seems her dementia is much worse. She is under hospice care but gets around with a walker. She seems to not remember my daughter now and also has come out of her room with only one clothing item on, thankfully he nurse on duty turned her around and took her back to her room to finish dressing. She is nothing like this, she would never do that before the dementia took over. Did another UTI test and it was all negative so I guess there is no stopping this. She is almost 94 so I imagine we just have to accept the fact that this is the road to her end..
Hospice workers probably know as well or better than anyone the signs of going into the final hours. But they were extremely surprised when I called to inform them of my husband's death. They thought at that point he had several more weeks to go. So clearly they are not always right and no one has a guaranteed schedule. They are very good, but not perfect, in being able to predict timing of death.
Any family members who want to see your mother should visit now. If it turns out she improves and gets off hospice, the visit will have been a bonus. But all should consider that the end may be near.