How long does a patient on Dialisis generally have to live?

That is a really hard question. A lot will depend on her general health. How willing and/or able she is to

do the treatments necessary to keep her kidneys normal. Does she have reliable help? Are there close friends that visit frequently? All these things will affect her will to live. Is she living alone or in a rest home or maybe with family. Is she happy with her lot in life? That last question may seem weird but I've found that people who have nothing to live for usually don't live long.

Does she have an understanding Doctor who will help her with pain relief. One that she feels free to talk to about the wrinkles and pains that accompany this disease. Many Doctors have knowledge but lack basic understanding of the things that are really important to the patients.

It varies quite considerably...

The significant information you supplied is that she is 87...

I am not in any way qualified to give you an estimate for her response to the dialisis...