My grandmother has end stage four kidney disease, heart disease, does not eat properly, is not dialysis, needs oxygen but doesnt use it, has diabetes and does not take her insulin, and she is in her late sixties. based on this, long does she have?

There is one typo in your statement I assume. End stage renal disease (ESRD) is stage 5 chronic kidney disease, not stage 4. When patient reaches ESRD, Insulin may not always be necessary. Survival varies a lot and the most important fact is oliguric (not making enough urine) or non-oliguric CKD. She survives much longer with non-oliguric type. Her time could be in the average of 6 - 24 months.

No one can predict that accurately. It is commendable you are worried about her. Best is to find someone e.g close friend, doctor or any relative to try to convince her to take care of herself. Good luck.