She has lost all concept of how to get dressed, loses body functions, quieter than her normal, wants to sleep an aweful lot, has no concept to put medicines in her mouth, stability worse (shuffles slowly and with effort with walker). The only thing she continues to do well is eat.
As you know, dementia is a progressive disease -- which means it gets worse. Sometimes it gets worse very gradually and steadily. In many cases it takes a sudden nosedive and gets very much worse all at once. And then it may stabilize at that worse level. Eventually the decline will lead to death.
This is a very tough wait-and-see situation, but I don't think there is a lot more you can do to find out her prognosis.
My parents use to brag that they only needed 6 hours of sleep at night.... yeah right, they didn't count the nap they both took on the sofa for a hour after breakfast... the hour nap after lunch... the hour nap prior to dinner and again after dinner. Any time I visited them, at least once a week, I had to go wake them up.
Has Mom fallen recently? Would she tell you if she did? My parents use to hide Mom's falls. On Mom's final fall, scans showed a current and past brain bleed, and such head trauma will spiral a person into late stage dementia. My Mom went from someone fairly sharp for being 98, to being someone who couldn't do anything for herself, all within a couple of days. My Mom had refused to use a walker.
Twelve years ago I lost my boyfriend of 12 years to lung cancer. He was the true love of my life but I handled the grief of losing him much better because he was actually gone physically. His death was final unlike the death of a person who has dementia who is still living and breathing but is unrecognizable to you. Once I realized that grief was what was keeping me moving on I could approach my depression in a more realistic manner. I do not know how long it will be before my husband physically passes but I pray every day that some night he will go to sleep and just not wake up so that his suffering will come to an end and he will be free once again.