My mother, 89 years old, is in a hospice facility and was recently diagnosed as being in "end stage Alzheimers." She had been in an assisted living facility, but was transferred to the hospice because the other facility determined that they could not do anything for her.
https://www.agingcare.com/articles/stages-of-alzheimers-disease-118964.htm
People don't usually go from diagnosis to end stage in under a year, in fact 5 - 10 years or more is the norm. I don't know what is going on with your mother but it sounds very confusing.