Ok, I've done some work on the family now. While it's not confirmed yet, I lean towards the theory that John David Maggard is her father, based on the marriage record that I found between Polly and William Casebolt. The marriage was conducted in the home of "John D. Maggard", and the officiant was Rev. Samuel Maggard. Apparently John David Maggard's father was one Rev. Samuel Maggard. So it lends credence to that theory, but more research is needed.