I agree with everything mentioned above, and will just look at your question from a little different angle.
The suspension of disbelief is what every work of art that attempts to be realistic tries to create in the reader's mind. In other words, a realistic story must get the reader to believe that the story actually occurred in real time some time in the past. Consciously, any reader knows fiction is made up. The writer's job is to make the realistic story seem real.
Writer's can do this in numerous ways. I'll just mention one important method Walker uses to accomplish this in "Everyday Use."
Verisimilitude is the use of concrete details to make a scene seem actual. Sometimes numerous details are used, and sometimes just the right one detail can accomplish verisimilitude. Notice Walker's opening paragraph:
I will wait for her in the yard that Maggie and I made so clean and wavy yesterday afternoon. A yard like this is more comfortable than most people know. It is not just a yard. It is like an extended living room. When the hard clay is swept clean as a floor and the fine sand around the edges lined with tiny, irregular grooves, anyone can come and sit and look up into the elm tree and wait for the breezes that never come inside the house.
Technically, a writer could have simply said something like: I will wait for her in the yard.
But a writer must make her words be more than just black ink on white paper, and a writer does this with details.
The yard is not just a yard. The speaker writes that she and her daughter made it "clean and wavy yesterday," creating an image and giving the action a time--yesterday. Another image is created by the comparison: "It is like an extended living room." The "hard clay is swept clean as a floor," and even the sand on the edges is given grooves. And people come sit in the yard and look up at the tree and feel the breezes.
These details create images and verisimilitude and lead to the suspension of disbelief.
That way, when Dee arrives at the house, it will seem to the reader that she is really arriving, even though she herself does not notice the yard that the mother enjoys so much.
I would say that there is almost no need to suspend one's disbelief when reading this story. This is because the characters and the setting seem completely believable, at least to me.
At the time that this story was written, it is not hard to believe that there would be black people living in the South in the conditions that Mrs. Johnson and Maggie live in. It is also not hard to believe that they would not have heard of the Arabic greeting that Dee's boyfriend uses.
It is not at all hard to believe that Dee and her boyfriend would act this way since college kids often think they understand way more than their parents do, especially if they are from families that lack education.