I've looked through the Pitner information that I've got, which was compiled by a Pitner cousin. He suggests that the Pitners in Knox and Sevier County Tennessee which have not been attached to the family tree yet, are descended from John Pitner, b. 1762 or 1763 (place unknown), son of the immigrant John Pitner who was supposedly born near the city of Coblentz on the River Rhine in Germany.
This second John is the brother of Michael Pitner, from whom the Illinois branches of the Pitner family descend. John married Elizabeth Fifer on 16 November, 1788. Their son Adam was born 1789 in Tennessee. No other children have yet been identified, but your Becca might be descended from an as yet unidentified brother of this Adam. The family lived long in Tennessee, but John, his wife, his son Adam, and Adm's wife Rachel Campbel are all buried in Sautee, Georgia, and it is from this Adam that many Georgia Pitner's descend.
Another possibility would be the family of Adam Pitner (b. abt 1766 in Virginia, son of the immigrant John Pitner), whose son John, b. abt 1800 lived in McMinn County Tennessee, and was buried in Whitfield County. This John married Sarah McCaugay. I don't have any info. on this John's siblings or his children, but it is another possibility.
If you have any more specific county information, it might be easier to figure out which family to focus on.