Can someone explain to me stages of dementia?

I think it depends on the age of the person. Here's a lik to an article on this website. The Stages of Alzheimer’s Disease https://www.agingcare.com/articles/Stages-of-Alzheimers-disease-118964.htm

It's pretty unclear when someone moves from one stage to the next. How old is your loved one? Does she have other illnesses? What kind of behavior and memory problems does she have?

Don't feel bad if you sometimes wish she would just go ahead and die. That's a pretty common feeling. As long as you do nothing to hurry her along!