I think you have started off on the right lines at least. Clearly, the intial part of "A Rose for Emily" speaks a lot about Miss Emily Grierson and her standing in the community. One approach to this question is to consider the way that Miss Emily is presented as someone who, in a sense, was already dead or at least not really living before her death. Note how this is indicated by the description of how her house and its locality has declined in recent years:

...set on what had once been our most select street. But garages and cotton gins had encroached and obliterated even the august names of that neighbourhood; only Miss Emily's house was left, lifting its stubborn and coquettish decay above the cotton wagons and the gasoline pumps--an eyesore among eyesores.

Just as Miss Emily's house is now an "eyesore" though it once was on the "most select street," so too has Miss Emily herself exited life and declined in her public standing. Note how we are told that no one had entered her house for more than ten years. She is a piece of history, and one who hasn't really beenn living life for a long time: ever since she killed Homer Barron and was united with him forever in his death.