This is the only Mintrel(l) Henry in the 1900 census index:
1900 United States Federal Census > Indian Territory > Chickasaw Nation > Township 7 > District 149 > Page 12B
Dwelling 198/Family 202
Marinady Ryle, head, white, male, b June 1819, 880, widowed, b KY, parents b SC, farmer, reads, writes
Coley Watts, daughter, white, b Jul 1873, 26, married, b Missouri, parents b KY, reads, writes
Wathan Watts, son-in-law, white, b Aug 1872, 27, married, b Indian Territory, father b Indian Ter, mother b Mississippi, reads, writes
James Ryle, son, b Sep 1875, 24, married, b Missouri, parents b KY, farm laborer, reads, writes
Mintrell Henry, boarder, white, b Jul 1878, 21, single, b TX, father b LA, mother b Alabama, reads, writes
Campbell Anderson, boarder, white, male, b Sep 1875, 24 single, b TN, parents b TN, farm laborer, reads, writes
You should also try to get Mintrel's death certificate.This page shows more information on how to do that: http://vitalrec.com/az.htmlhttp://vitalrec.com/az.htmlHer death certificate should give the names of her parents to the best knowledge of the informants.If the death certificate lists a Social Security Number, you can then order her Social Security Application, which she would have filled out, and which should also list the names of her parents.
If you want to try searching the 1880 census yourself, you can do so for free at www.familysearch.org or www.ancestry.com.