Jackie, none of Mary HOCKERs I have with a birth date around 1833 married a KNEPPER. The ones that I don't have a spouse for, I've located in 1850 census records in Pennsylvania. None of my information appears to match what you have.
I can say that George and Barbara (MARTIN) HOCKER had 10 children between 1833 and 1853, Mary being the eldest; and all of them were born in Dauphin County. This doesn't work with your Mary, daughter of George and Barbara HOCKER, travelling to Ohio in 1840 at the age of 7.
Mel Kelley and I searched for possible HOCKER parents of this Mary in Dauphin County and didn't get very far. Mel also found evidence to suggest that Mary's maiden name was not really HOCKER, but HAWK. I would try to connect with her for additional information.