What happened to Granny when she was 60?

From the text:

When she was sixty she had felt very old, finished, and went around making farewell trips to see her children and grandchildren, with a secret in her mind: This was the very last of your mother, children! Then she made her will and came down with a long fever. That was all just a notion like a lot of other things, but it was lucky too, for she had once and for all got over the idea of dying for a long time.