I'm not sure where she fits in. I see that their marriage bond was posted by Daniel Karker (Karraker). There was a Daniel Karraker who was the husband of Rachel Blackwelder (#543 in my Blackwelder database at
http://arslanmb.org/blackwelder/blackwelder.html), although this Daniel Karracker (born in 1793) had settled in Union County, Illinois by the early 1820s. Perhaps Rachel was an aunt of Mary. Have you found Mary Blackwelder and Moses Sides in the 1850 census or later? If you can provide me with the census citations, perhaps I can find a clue to link her to the Cabarrus County Blackwelder family.