Based upon the 1885 birth date of your GG-grandmother, here are the only candidate female Days in Butler County that might be your missing GGG-grandmother: In the 1870 Census for Butler County, there are only two Day households with young Day females:
1. Sarah, born AL about 1869, daughter of William Day (b.1817)
2. Martha, born AL abt 1860, daughter of William Day
3. Ellen, born AL abt 1852, daughter of Thomas Day (b.1819)
4. Mary, born AL abt 1850, daughter of Thomas Day
Knowing the early marriage customs of the day, I would bet on Sarah who would have been 16 in 1885.
Have you had contact with Joyce Parnell McCullough? She also has a Day connection, but her Day family is in Loundes County AL. She published a book on her Parnell family. You need to contact her.