How long could a person live with mostly clogged arteries?

We were just told that my mother who recently suffered a heart attack has 1 artery completely clogged and the other 2 are 95% blocked. They said that since she has diabetes that it is a full artery clog not just a section. I'm worried she can't last long like that especially considering she is immobile, on dialysis and has had strokes. Obviously no one can say how long she has, I just want to get a few opinions or personal experiences. Thanks