"England Births and Christenings, 1538-1975," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:N5ZP-94R : 30 December 2014, Mary Chown, 31 Jul 1796); citing SILVERTON,DEVON,ENGLAND, index based upon data collected by the Genealogical Society of Utah, Salt Lake City; FHL microfilm 916,935.
Parish marriage register (Zeal Monachorum) via findmypast
It may be possible to confirm family relationships with Mary 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 Mary: