Sarah Unknown ...
She married John Lowder likely before 1789 and may have had four or more children with him. (According to one family tree she had no children with John and was his 3rd wife, with the first one being unknown.)
In May 1839 she petitioned the Guilford County Court of Pleas for ownership of land that had been owned by her late husband, John Lowder, who had died without a will on May 1, 1839.
She passed away in 1842.
"North Carolina Estate Files, 1663-1979," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:Q2Z7-31YC : 17 March 2018), John Lowder, 1839; citing Guilford, North Carolina, United States, State Archives, Raleigh; FHL microfilm .
Among the documents I found at Ancestry.com is a Guilford County, NC Count of Pleas for the May term of 1839. There is a petition of Sarah Lowder in regard to some land owned by her late husband John Lowder (maybe 3,531 acres) "who departed this life intestate on the 1st day of May 1839".
This document shows that Sarah was his wife at the time of his death (not Mary) and It is clear which John Lowder she was married to because of the date of his death.
In a separate document, dated 16 August 1842, William D Anderson, Joel Lowder & William Chappel were appointed as administrators of the estate of Sarah Lowder, deceased. (William D Anderson was a son-in-law and Joel Lowder was a son) This is evidence that her death was likely sometime in 1842 rather than 1839.
I have not found clear evidence that John Lowder married Mary Ozburn in 1803. I found a handwritten record of a marriage between "John Landen" and "Mary Ozbun" on that date. This is inconclusive to me. ((Written and researched by Mike Hillyard.
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The record of a marriage between a Mary Osborne and John Landen in a different county in 1803 looks like it may have been attached to John Lowder because one of the 3 times that the name is written the name could be understood as John Lowder. Whoever the person was, he signed with a mark.