How could the characters have acted otherwise in Everyday Use?
I just don't know for sure what you're after here. "Everyday Use" is a work of fiction. They could act any way that the author wanted them to. As they are, they can't possibly act any way than what they do--it's a story. These people are not real. Art is artificial. It's not supposed to be real. They don't have free will--they're characters in a work of art.
Even if you're asking something like:--"If these people were real, how could they have acted differently?"--you could still punch in anything you want. Wangero could have been an axe murderer. Maggie could run up to Dee when she arrives and jumped into her arms. The answers are limitless. If this is really an assignment you have to do, write in anything you want.
Dee could have understood that her mother and Maggie possess their own kind of dignity and don't need outsiders coming in and telling them how to live. The mother could have not been so flippant and made jokes about her guest's name. Dee could have seen her upbringing as more that just quaint and artistic. Again, the possibilities are endless.
The characters could have acted otherwise because people have free will. Just because people have different experiences does not force them to misunderstand one another. Just because one person has gotten "ahead" of others doesn't mean she has to act like she knows more than them.
In this story, Dee (Wangero) and her boyfriend are the ones who really could have (should have, in my opinion) acted differently. Sure, it's easy to be arrogant when you're that age and are in college, but you don't have to be. So I think Dee should have been more humble.