I found the marriage of Nancy Seaver to Zenus Horton on 5 Dec 1799 in Windsor, Windsor Co, VT in the VT Vital Records last Saturday (I have the film at the local FHC, but have not reviewed all of it yet).
That's the good news - the bad news is her parents were not on the record, and I don't have her in my database. There are several Seaver families in the Windsor County area around 1800. After I finish all of the VT VRs, I may have a better idea of who her parents are.
In the meantime, would you please contact me by email firstname.lastname@example.org
and tell me what the names of Nancy and Zenus Horton's children are. Do you have a death record for Nancy? She may be in the VRs with parents listed.
Regards -- Randy