This is a person you don't actually know much about but see almost all the time. Since Elly is known to wear blue dresses, let's us her as an example of what I'm talking about. To most of the people in town, she's not so much a person as she is a sort of prop or set-piece that they'd miss if she were not there. They have no real idea who she is, where she came from and what she wants out of life but they do know that she has certain habits. She jogs and rewards herself with a coffee and doughnut. She has a large dog that she has trouble handling. She's got adult children that took a lot of time moving out and for some reason, they were reluctant to move any farther than thirty minutes away from her. She used to work at the library and at a book store but now, she's volunteering with her husband who used to be a dentist. She tends to yell a lot in public but doesn't notice that people are staring at her when she does it and they'll never really know why.
This is because she's not part of their daily lives and her eventual disappearance isn't going to shake their worlds but when she goes, a familiar chunk of the landscape will go away and that's going to be a bit of a downer. They'll wonder who she was and why she never seemed to get any farther in life than obsessively sweeping a back porch and hope that they themselves aren't being thought of as 'that old lady who never seemed to smile much'.