Early Hampshire County VA (now WV) TaxLists contain both Samuel Abernathy Sr and Samuel Abernathy Jr for the years 1802 to 1811 and 1813. In 1812 only Samuel Sr is listed. The IGI cites Susan as a daughter of a Samuel & Mary Abernathy of Hampshire County, but has no source data. Which of the two Samuels listed on those tax lists and on the 1830 Hampshire Co., VA Census is questionable, but it's most likely to be the elder of the two. I've seen her birth estimated as 1790 and as 1793. Location either PA or VA. If her father was Samuel Sr, then his parents were likely to have been William Abernethy & Sarah Samuels, who arrived with parents in the Pennsylvania area probably no later than about 1730, maybe as early as 1720. William is found in Cumberland Co., PA court records, 1750-1761. He signed his will 24 Sep 1780 in Frederick Co., VA. The family appears to have come from Northern Ireland: William was Irish, and, I think, Presbyterian.
It is possible that somewhere in one of the libraries in Ohio or Indiana you might be able to find a copy of "Ancestral tracks to Clermont-- and beyond: Hutchinson, Abernathy, Shade, Needham" by Mary Ann Needham Hollifield. I don't have a copy; it was privately published in 1996, ran to 1050 pages, and may no longer be available, but I am given to understand that it was a thorough study of this family and allied lines, so it's probably worth trying to find.