I think one element about Granny Weatherall's character that comes across incredibly strongly is her independence and inner-strength. Part of the reason why she is so cantankerous in her near-death state is because suddenly she has to be dependent after years of being independent. Consider one of her memories of her life before getting old:
In her day she had kept a better house and had got more work done. She wasn't too old yet for Lydia to be driving eighty miles for advice when one of the children jumped the track, and Jimmy still dropped inand talked things over: "Now, Mammy, you've a good business head. I want to know what you think of this?... Old. Cornelia couldn't change the furniture around without asking. Little things, little things!
We can see then that Granny was considered capable, intelligent, and reliable; her grown children came to her for advice and she is immensely proud of her homemaking skills and her capacity for hard work. We can see then that these qualities have a massive impact on her outlook on life as she looks at life through her "lens" of independence and inner-strength, so that at the end of the story, she meets death with the same customary strength as she has shown throughout the entire story.