You think they were born in Tennessee even though the Census shows that Gillam was born in South Carolina and Sarah in Mississippi?
I looked for their marriage in Jasper County, MS but didn't find it in Ancestry nor in FamilySearch. If you think they were married there, you can contact the local genealogical and historical societies about their marriage license.
You can contact the Jasper County MS genealogical or historical societies about her death and burial info. Successful Searching!