I have spend the past several hours reading your posting history. This looks like a hundred years of work!I am truly in awe!
Although it does not show up in your own family history, numerous Wilburns were also allied with many of your ancestral families.
My hunch is that Mary Wallen is a descendant of the Elisha Wallen family.I am not a Wallen researcher, but Wilburns and Wallens and Blevins were allied families for many generations.(Side note here: I notice in your Cogswell line that you also have Mary Wallen. James Wilborn b. 1844 is living with a Cogswell family in Fleming Co KY. 1850 census.
If you log onto the Wallen line I am certain that some of the seasoned researchers who connect to Elisha Wallen will be glad to fill in the blanks...It does seem highlythat Mary Wallen is from this same line.(From the top of my head, Elisha Wallen b. 1708 m Mary Blevins..One of their sons -Elisha Wallen b 1734- was a noted Long Hunter of then similar status as that ofDaniel Boone.