A good solid question. Miss Emily's house " had once been white": like Miss Emily, it has been stained and even tainted by time. (Think of how she became.) It is " 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." Like the house, her style and time have passed. They used to be important; now they are not. What's more "garages and cotton gins had encroached": like the house, she is crowded by change and commerce. She's a relic and out of place. Finally, "only Miss Emily's house was left, lifting its stubborn and coquettish decay": the house and its own remain unnaturally flirty despite the time, making it, and her, "an eyesore
among eyesores." Yes, she's repulsive, but so is the town.