I descend from Thomas Carleton Puryear's brother John. In her book on the Puryear Family, Grace Hollis Puryear had the following to say about Thomas Carleton Puryear. "Thomas Carleton Puryear, b- ca. 1790, Mecklenburg County, Va. m- Mary Moorehouse.A son of theirs, Peter Puryear, m- Martha Ann Jones and they were the parents of Sarah Puryear who married Early H. Epping of Columbus, Ga. Sarah's DAR# 42173 contains some errors regarding her Puryear ancestry. Some descendants of Thomas Carleton Puryear changed spelling to Preer." That was all she had to say about that family.
I believe that your Susan is the female child under 5 years of age who was enumerated in the 1840 census for Carroll County, Georgia. My research shows no other possibility of her being the child of any of the other descendants of William and Rebecca Carleton Puryear.
Susan's brother, Thomas C. Preer(born bet 1815-1820 in Georgia), married Agnes Elizabeth Church on 12/7/1841 in Troup County, Georgia. Thomas seems to have died before 1850 as Agnes E. Prier is in the 1850 census for Troup County with her two children. Agnes is living with her son Thomas in the 1870 + 1880 census for Chambers County, Alabama.
You seem to have all the info on Susan's brother Peter.
Susan's brother, Charles B.(or D.) Preer, is in the 1860 census for Barbour County, Alabama.