(I am not a medical doctor, this is not medical advice.)

Dialysis is actually a pretty extreme intervention, isn't always an option, and doesn't actually guarantee continued life. Life expectancy of patients on dialysis is generally 5-10 years. It's a pretty big lifestyle committment, too, like 3-5 hours per session, and 3-7 sessions per week. Certain other issues like stroke, heart disease, lung disease, or cancers could even preclude dialysis from being a medically sound recommendation.

Even if she might be a good candidate for dialysis, she also has the right to choose not to do dialysis if she doesn't want to. If that is the case, I don't think it would be right to criticize that choice. People have the right to choose to die.

Having said all this, doctors generally can't and shouldn't give you such a precise estimate on lifespan, and a handful of days is really quite uncommon. It would be extremely unlikely for a doctor to tell someone that they will die in such a precise time frame as exactly 4 days, somehow ruling out 3 days or 5. However, it wouldn't be so uncommon to tell someone they may survive only a few days or weeks without dialysis.

Such a precise and close timeframe, associated with ESKD simply doesn't pass the sniff test: there is some missing or incorrect information here. I think the most likely possibility is that she shared her misinterpretation of a terminal diagnosis.

My guess is the doctor said something like "You can survive a week without emergency plasmapheresis." A lot of people tend to instantly check out as soon as they hear "a week to live" or something similar. It's not uncommon for people to panic about things like this and entirely miss the other half of the sentence.