I have a probable match for you with Martha Boyd Abernathy. I have only two Martha Abernathys born between 1900 and 1910 in my database, but only one was living in Chambers County on the 1910 & 1920 census, with parents. I believe she is the one you have married to Henry Lewis Jarrell. The Abernathy family she is shown living with (as a daughter) was clearly Baptist, as well. The other Martha Abernathy I have in that timeframe isn't even in that state.
*IF* (which I cannot swear to) she is in fact the one you're looking for, her parents are in my database as Lucius Hugh Boyd Abernathy and R. Mittie Sorrell. I have only approx birth dates for either. However, they married 27 Jan 1897 in Chambers Co, AL, service performed by Geo W. Hall, T.D. [source: Alabama Marriage Collection, 1800-1969, found on ancestry.com]. Alabama Death Records (1908-1959) on ancestry show Lucius died 20 Apr 1950 in Tallapoosa County, AL.
Lucius can be found with his parents on the 1880 Chambers County census, in Chappell Hill. On the 1900 census, he is residing in Hamburg, Chambers Co., AL
His Father, David Hugh Boyd Abernathy, was born 4 Jul 1838 in Dekalb Co., GA, and died 8 Feb 1931 in Chambers Co., AL. He is buried in the Macedonia Primitive Baptist Church Cemetery, Chambers Co., AL. He served the CSA in the 147th AL Infantry during the Civil War. His parents were Samuel Abernathy (1798-1878) and Jane Boyd (1799-bf 1880). Samuel is also buried in the Macedonia Primitive Baptist Church Cemetery, as is his Mother.
Samuel's parents were John Abernathy (d. 1807 Newberry County SC) and Rhoda Davis (1759 Newberry Co., SC-7 Nov 1843 Chambers Co, AL). I have no idea where in SC John is buried, but Rhoda is buried near her youngest son, Samuel. If John served in the Revolution, his direct descendants have not yet uncovered any proof of that.
It is presumed but not proven that John's Father may have lived in PA before moving south into the Carolina area.
This lineage is clearly not very closely related to any of the other major or minor Abernathy lines so far tracked here in the United States, although scattered descendants are found in most of the Deep South States.