Dramatic variations in cognition, capabilities in Stage 7

My 97-year-old mom has been in late Stage 7 of Alzheimer's for over a year now. On bad days she can't sit up, needs to be lifted into and positioned in bed, needs to be spoon fed pureed food, chipmunks food, often chokes, and when she speaks her words come out as gibberish. Her limbs thrash. About four months ago an old friend visited and she was mostly unresponsive the entire time and the friend left in tears.

On good days she can read and converse intelligibly, follow TV, enjoys a hearty appetite and feeds herself, swallows just fine, laughs and smiles a lot, enjoys having her hair done, sings along to music, has good color in her face. Yesterday she was scolding me for wearing jeans and not dressing up when I visit. She tells the hospice nurses entertaining stories about old friends.

About a year ago hospice nurses told me she was near death. She really did look like she was dying. Her face had that stiff mask-like pallor of death. She was struggling to breath, on oxygen and mostly unresponsive for over a month. Then she suddenly boomeranged into a period of lucidity, hearty appetite, etc. They told me about terminal/paradoxical lucidity, how loved ones often enjoy brief periods of good cognition and lucidity shortly before death. But periods of terminal lucidity last only hours or at most a day. My mom's good periods have been stretching into weeks, even months.

I described to a friend who's worked as a memory care aid for many years how my mom has been swinging between these stages of incapacitation and unresponsiveness with months-long intermittent periods of fairly good cognition and lucidity. She claimed she'd never seen anything like it.

Any ideas what might be going on? My husband has grown convinced that my mom doesn't really have Alzheimer's and we've been mistaken all along.