MITCHELL (all b C W, C of S): Alex 37 marr. foreman and pilot; Agnes 34 marr. ; Assumed children: James 14, Mary Jane 9, John 7, Agnes 6, Isabella 2; Previous hsehold George & Agnes (nee WiLLIAMSON) SMITH incl. Jane FAIRBURN 65 single b IRL (nee WILLIAMSON, sister to Agnes SMITH and believed mother of Agnes MITCHELL) 
↑ Source #S403: 1861 Hawkesbury, Prescott, Ontario; Roll: C-1068, hsehold of Alex & Agnes MITCHELL
Source S403: 1861 census of Canada - images via Ancestry.com
It may be possible to confirm family relationships with Agnes 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 Agnes: