The Cameron Genealogies website https://clan-cameron.org.au/genealogy/getperson.php?personID=I57948... shows Rachel MacGregor as being married to Ewen Cameron on 20 Feb 1804 at Fortingale, Perthshire and subsequently living at Rannoch. I don't know which details are correct.
Rachel's father, Donald MacGregor of Lerrigan, is thought to be Rorie Buidhe (Yellow Rorie), son of James Mohr MacGregor (Rob Roy's eldest son)