Margaret was born after 1800. She passed away after 1860.
"United States Census, 1850," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MCDK-F3N : 12 April 2016), Margaret Horner in household of John B Horner, Jefferson county, Jefferson, Tennessee, United States; citing family 114, NARA microfilm publication M432 (Washington, D.C.: National Archives and Records Administration, n.d.).
It may be possible to confirm family relationships with Margaret by comparing test results with other carriers of her mitochondrial DNA.
However, there are no known mtDNA test-takers in her direct maternal line.
It is likely that these autosomal DNA test-takers will share DNA with Margaret: