I have not been able to locate Andrew in the 1880 census. He would be about 16, and he isn't with his parents or any other Rowan Co family. Probably he was out working somewhere; doing itinerant lumber work or something.

Ella is the Ellen age 18 in the following family:

1880 census of Rowan Co., Ky, Pine Grove precinct, lists as family #202:
Easton, Jas F., 46, farmer, Ky Eng Ky; Elizabeth, 41, wife, Oh Ire Pa; Martha, 22, dau, teacher, Oh Ky Oh; Ellen, 18, dau, Ky Ky Oh (dittoed for all younger children); Jas W., 16, son; Francis B., 14, son; George Ann, 11, dau; Robert W., 10, son; Laura M., 6, dau; Lilly F., 3, dau.

I am not entering her parents or other family members into the database unless one of her siblings besides Ella gets entered because of other links.

Rowan Co. marriage Book 1, p. 32, records marriage on 10 Mar 1883 of Andrew H. Cornett and Ella Easton. The marriage is also recorded in Book A, p. 59, on 12 Mar 1883. (From index only; I haven't examined the originals. The very rough age for Andrew is estimated only assuming he was probably age 18 - 33.)