I believe I know of another daughter of Gabriel, Elizabeth Alexander, who married Peter Mock (Jr.).
A report on a North Carolina property transfer reports: "1810 a. land inherited by Eliz. Alexander Mock from either or both of her parents.. solt to Robert Templeman husband of Rosana Alexander sister of Eliz."
I have further information on the family of Peter and Elizabeth.
Owen Mock, descendant of Peter Mock and Elizabeth Alexander.