Margaret & Delilah Couch were sisters. Delilah died less than a year after she & Charles were married without having any children (at least none that lived). They married Sept. 14, 1842........on Sept. 3, 1843 he married her sister, Margaret Couch Williams. She was a widow with a 5-year-old son, William A. Williams.
I don't recall seeing "Margaret D." on a census, but I haven't looked at them in a couple of years. Which Census is that on?
My great-aunt (granddaughter of Charles & Martha Pierce Bethany) said one of her aunts was named Diane or Diana, but I've never found her on a census. However, there was a Nancy D. and I feel her middle name was probably the Diane/Diana my aunt mentioned. Maybe that was Margaret's middle name too.
Also where is Shady Grove Cemetery? That might give us some leads on Delilah's burial and where Charles lived before he married. I have not been able to find either of those.