I did find a Land Petition which I think might fit here:
Digitized Microform NAC c-2193 p 77,78,79. Petition #20 1798 Cornwall for a "Kitty" McMillan married to Donald McMillan who says she is a daughter of Alexander McDonell a Loyalist of Cornwall. Note from Neil McLean J.P. : "Catharine McDonell is the dau of Alexander McDonell a Loyalist who came to this counry in 1780".
I did find the Land Petition of Lauchlin McDonell son of Angus McDonell UEL