Do note that ansteynomad initially said:
"George Aucott's 'wife' Charlotte"
I don't think anyone is alleging a marriage.

... Oh oops, I seem to have made that assumption back in 2013. Don't tell me I'm the source of the entire confusion! (I thought ansteynomad was speaking from knowledge of Charlotte, but you may have been just quoting my old post.)
I think the "sister" hypothesis makes sense, maybe especially because in 1870 both George and Charlotte are shown as widowed. (I suspect this more specific info, i.e. on the 1870 image, wasn't available or was behind a paywall back in 2013.)
I'm irrelevant here, but what I'm not seeing is the baptism of sister Charlotte Aucott. She has a grave, though, and the info given there ties her in as sister:
https://www.findagrave.com/memorial/147627042/charlotte-aucottSo then it would out that you two actually are related, sharing the parents of George and Charlotte as your mutual ancestors!