Dear Daniel,
Here is the 1880 census entry for Ann Esselstyne and Estella Brown, with others, in Kinderhook, Columbia, New York.
"United States Census, 1880," database with images, FamilySearch(https://familysearch.org/ark:/61903/1:1:MZZJ-WYC : 20 August 2017), Ann Esselstyne, Kinderhook, Columbia, New York, United States; citing enumeration district ED 21, sheet 374B, NARA microfilm publication T9 (Washington D.C.: National Archives and Records Administration, n.d.), roll 0821; FHL microfilm 1,254,821.
Maybe looking for the Keegan family would help you find Estella in later years? Hope this helps! -NGP