There was another line of McClanahan family around Smith County, TN, so Mary Frances was probably not a part of the line that went to Mississippi earlier. McClanahans were spread out from Adams Co., OH, Mason & Bourbon Co., KY to Shelby Co., AL, and many counties in between. Many were based in Virginia during the 1700s, but I'm focusing on those from South Carolina. Simpso Co., KY, Rutherford and Hickman County, TN might be your best bet for links to Mary Frances' family.
John McClanahan