The grandmother in "A Good Man is Hard to Find" gives great importance to being "a lady," and her ideas about what that means reflect an old-fashioned, somewhat upper-crust Southern mindset. She uses the n-word and longs for the good old days when kids were polite, people were trustworthy, and there were pretty plantations to visit. All of this leads her to associate being "good" with coming from a respectable family and behaving like a member of her social class; those who don't are outsiders. Her sensibilities are in for quite a shock when she meets The Misfit.
The grandmother's values are only concerned with appearances, and are therefore criticized and mocked by the story.