Her name is listed as "Nicy" on the marriage bond.
Nancy died around 1859 possibly from complications related to the birth of Houston. After her death the children were spread out with other family members to be cared for. The clue to these childrens' parentage was in the census records. Listed under the families of James D., Abraham and Jonathan H., their ages were out of order with the other children. This slight out of sequence hint helped solve the mystery of the children of Nathaniel and Nancy. It is suspected that there are other unidentified children between Lucinda (1852) and Nathan D. (1857). They are possibly listed with their aunt, Levicy, and I suspect they will be found as more census records are located.