Margaret Chastine- Dekalb County, Al

I am searching for the parents of Margaret Chastine(Chastain, Chasteen, etc).She was the first wife of Walker Stewart and died shortly before the 1850 Dekalb County, Al census was taken.She left one son, John, who listed his mother's birthplace as South Carolina.Margaret's surname was listed as "Chastine" in CW pension papers.The best I can ascertain is that her father may have been Abner H. Chastain of Walker County, Ga.Any information would be appreciated.