This may put an end to the Gibson theory - from WorldConnect - 1794 will does not mention a daughter married to a Mowrey except Mary, wife of Henry:
Wills of Alexander Gibson
Note: Alexander Gibson had two wills, written 12 years apart entered into Augusta County court records:
Page 178.--15th July, 1782. Alexander Gibson's will--Executor, son Alexander; to wife, Mary, to be maintained by son Alexander; to daughter, Christian, unmarried; to daughter, Mary, unmarried; to daug hter, Margaret, unmarried; to grandson, Daniel Gibson; to grandchildren, Elenor McFarland, Daniel McFarland, John McFarland, Ann McFarland; to grandchildren, Isabella, Alexander, James, and Mary McFar land. Teste: John Elliot, Elizabeth Elliot, Elizabeth Gibson. Proved, July Court, 1795 (purporting to be a former will), by John and Elizabeth Elliott and recorded on motion of Alex. Gibson, Jr.
Page 171.--6th September, 1794. Alexander Gibson's will--To wife, Mary; to children, viz: Elizabeth, Christian, Mary Mowrey, Margaret; to grandson, Daniel Gibson, who is to make deed to Daniel McFarli ng for his tract on Christian's Creek; to John McFarling; to grandson Edward Atkins; to granddaughter, Sarah Allen (I believe is her name, but Mrs. Haladay knows her); to granddaughter, Ann McFarling; to granddaughter, Elizabeth Congo (Cargo?); to grandson, Samuel Cargo; to Daniel McFarling. Executors, Robert Porterfield, Henry Mowrey. Teste: Jas. Hill, Daniel McFarland, Christian Gibson. Proved, 16th June, 1795, by James Hill, Daniel McFarlin. Executors refuse to execute, widow also. Administration granted Alexander Gibson, son to decedent.