One of the primary conflicts in "A Rose for Emily" by William Faulkner is between the present and the past. The past, of course, is represented by Miss Emily and her father. He raised her in the traditions and values of the Old South, and Miss Emily never really deviated from them, except for her affair with Homer Barron. She lived in the same way and in the same decaying house until she died, despite the fact that the world around her changed drastically.
The present is represented by the townspeople. They are the "we" to whom the narrator (presumably a citizen of the town) refers. Faulkner uses the plural here because it serves as a reminder that everyone else has changed and evolved with the times--everyone except for Miss Emily, of course.
The relationship between the people of the town and Miss Emily is also clear from the beginning:
Alive, Miss Emily had been a tradition, a duty, and a care; a sort of hereditary obligation upon the town....
Again, the relationship between Miss Emily and the town (the plural "we" to which the narrator refers) is adversarial, and this relationship shows in many ways, including the use of "we" versus "she."