I didn't find an answer, but I did find what appears to be another marriage for Sally Mullins. This might help you find her death certificate and maybe her parents names.
"After the death of Susanna Lay in 1870, Jesse Duncan Lay married Sally Loggins. She was the widow of Major Loggins who was killed in the Civil War. She was Sally Mullins before marriage; later Jesse Duncan Lay was again married to an Estes. Jesse Duncan Lay, died November 4, 1896, while still living on his “Water Fall” farm in Marion County, Arkansas, where he had owned and operated a grist mill at the falls on Water Creek. He and Susanna are buried on the Homestead near the Water Falls. She had ask that they be buried there."
http://www.olivehill.org/Lay_Family_Genealogy_JGilbertLay_ArkansasPages.pdf, page 90 of this document.
