yes, i understand your frustration. many people that develop serious health issues don't really accept their situation fully. some have a more difficult time with sudden and dramatic change than others. too many insist on keeping things the way they were when such a mentality can only lead to disaster.
dialysis is not a cure for kidney failure. it is a treatment. many die while on dialysis because they don't respect the fact that their life has changed.
the average life span of a dialysis patient is around 6 years (on dialysis). it is quite apparent that those who become known as 'the exception to the rule' are those who
take their condition seriously enough to make drastic changes in their daily habits. diet is very important to a dialysis patient and to purposly ignore the effects of food on the body is purely suicidal.
my condition is due to receiving a blood transfusion at the age of two to save me from pernicious anemia. in 1951, there was no knowledge of hepatitis C in canada, and some of that blood i was given contained that virus. it stayed with me for 50 years before knocking me down.
i hope your sister realises that she does have some measure of control over her health, but if she ignores the dietary restrictions that kidney failure demands, she is only hurting herself and her family in the long run and won't be around very long. denial is a long river with many bodies in it.

nevertheless, i wish you and yours
all the best

LL