Oh gosh, I'm sorry about your mom. I tis really hard to watch our parents health change and go poorly. My father in law had significant kidney issues and for him, the change happened relatively quickly until he started dialysis and then was stable until his death from other issues. We missed the boat in starting dialysis in a calm way as he had a dramatic health decline and was hospitalized. At that point, he had excessive swelling and they were taking liters of liquid from him, was hallucinating and very ill. Would have been nice to avoid that and start dialysis earlier. BUT, I do understand that this is a hard decision because from then on, it was receiving dialysis on a regular bases (three time weekly) for the rest of his life. He did this for about 5 years until his death. He had to incorporate a dialysis meal plan as well.
I think for everyone the rate of decline will be unique. Looking at the numbers helps but also symptoms and if a decline happens over hours or days, that's it. It needs immediate consultation. In general, chronic kidney disease progresses slowly. But at her age, other things could come into play and speed it up.
Also, I'd ask this question of her doctor. Does she live in assisted living?
Oh, I'm so sorry. That's such a horrible situation to be in. While you understand, I will tell you that my father in law did have a decent quality of life despite his dialysis appointments. He scheduled them for the AM and sat there for his couple of hours and then was his regular self the rest of the day and week. He was her age and did this. But Alzheimer's makes it more difficult. I do respect wishes but also you are probably her power of attorney to make medical decisions. It is a fair amount of poking for the dialysis as well. It was worth it for our family and he was resistant until it became clear without it he would die. Lung cancer too. Gosh, I really feel for her and you. I lost my mom at a young age which was tragic but dealing with the aging body is emotionally so very hard. How are you doing with all of this sweetie?