Mary was born about 1820. She passed away after 1855.
Sources
"United States Census, 1850," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MHJT-XPZ : 12 April 2016), Mary Brown in household of Saml Brown, Jefferson, Miami, Indiana, United States; citing family 751, NARA microfilm publication M432 (Washington, D.C.: National Archives and Records Administration, n.d.).