I hear about stages, how can you tell? I take my mom to a geriatric neurologist and ask him what stage she was in and he said hard to tell.

I always disliked the "stages" boxes
My Husband did many things that he should not have been able to do yet there were things that he could not do that according to the levels he should have been able to do. (If I were to use the boxes he was at stage 7 and stage 3 at the same time)
You can look at the stages and all the things listed and check off what can and can not be done and that will give you some idea but nothing with dementia is a hard and fast rule.
There is nothing that can be done to stop the progression.
You can kind of gauge what is going on, you can sort of tell what will fail next.
I would not worry about "pigeonholing" stages and be grateful for what she can still do at any point.

Fromzstore, I found these articles right here on Aging Care, hopefully you can find what you are looking for.

https://www.agingcare.com/topics/5/alzheimers-dementia/articles

It can be hard to tell what sort of a dementia a person has, let alone what stage of which dementia a person has definitely reached. All the more so if a person's condition is multifactorial, or if she also has other types of illness.

I sympathise with the natural wish to consult milestones and get your bearings, though. Have you had a look at alz.org? Their explanations of the various dementias are very thorough.