My FIL is in functional stage 6 of Alzheimer's. He has 24 hours home care which is expensive. I asked the home care nurse what to expect. According to them, when he gets into stage 7 in 1 year or more, he would be violent and throws food at you, and his diapers would need to be changed constantly; he would not know my husband and he would not care. He would object violently if you try to care for him. The most obvious sign is stop eating or needs to be fed. It would be the last sign and it depends on you or your Mom whether you or she would continue tube feeding. If not, she would be let go naturally in hospice. Or she would have pneumonia because she could not swallow at that time. They would not just go into a coma. Please check for more info. in the website www.alz.org  under staging.   Regards, Nina