I am not really sure whether Nancy is a daughter of James’ second wife Lucy Brammer, or his first wife Elizabeth Agee. If the birthdate on her gravestone and her age of 8 in the 1860 census are correct, then she was born about three months before James and Lucy were married. But if her reported age of 7 in the 1850 census was correct, then she was born after they were married. (And in that case, her sister Louisa’s birthdate would have to be later than reported as well.) But in any case, Lucy was the only mother she knew.

1870 census of Patrick Co., Virginia, Smiths River township, enumerated 21 Sept, lists on pp. 63-64 as family #473/501:
Dehart, Henry C., 30, works on farm; Nancy F., 27; Virginia T., 4; Missouri A., 2; Mentora J., 5/12. All born in Virginia.

1880 census of Floyd Co., Virginia, Jacksonville district, enumerated 7 June, lists on p. 9 as family #92:
DeHart, Henry, 40, farmer; Nancy F., 37, wife; Virginia T., 15, dau; Missouree A., 13, dau; Mentory J., 11, dau; Georgia G., dau, 9; Charley L., 6, son; Sally L., 3, dau. All born Va Va Va.

1900 census of Floyd Co., Virginia, Court House district, enumerated 25 June, lists on p. 14B as family #249:
Epperly, Levi G., 22, b. Sep 1877, farmer; Clara V., wife, 19, b. Aug 1880, married 2 years, mother of 1 child, 1 living; Lillian A., dau, 1, b. July 1898; Dehart, Henry C., f-in-law, 60, b. Dec 1839, miller (grist mill); Nancy F., m-in-law, 58, b. Feb 1842, married 36 years, mother of 7 children, 7 living. All born Va Va Va.

1910 census of Floyd Co., Virginia, Court House district, enumerated 4 May, lists on p. 7B as family #132/136:
DeHart, Henry C., 70, farmer; Nancy F., wife, 68, first marriage for both, married 47 years, mother of 7 children, 7 living; Weaver, William A., son-in-law, 42, carpenter & contractor house building; Georgie, dau, 37, first marriage for both, married 19 years, mother of 1 child, 1 living; Daniel, grandson, 14. All born Va Va Va.

1920 census of Floyd Co., Virginia, Court House district, enumerated 22 Jan, lists on p. 9B as family #184/185:
Dehart, Henry C., 81, farmer; Nancy F., wife, 77. Both born Va Va Va.