The narrator of this story is the voice of the town rather than a specific person. The story begins with a recounting of when Miss Emily Grierson died, and how the whole town went to her funeral. The women of the town went mostly out of curiosity to see the inside of her house, which is "a big, squarish frame house that had once been white, decorated with cupolas and spires and scrolled balconies in the heavily lightsome style of the seventies, set on what had once been our most select street."
The best answer for this question would be: That beauty can fade Shakespeare takes us on a romantic ride on his poetry about loving someone so dearly. He compares that beauty may eventually fade, but the spirit of youth will never go away.
Probably foreshadowing. It doesn't seem to be a flashback or symbolism. Tone doesn't seem right -- there doesn't seem to be an easily picked out tone. So, probably foreshadowing. We all know she dies in the end, here Shakespeare's just saying "hey, she might die, just so you know"