Responding to my own post here.
Thanks to Evelyn Goulet, I"ve learned that there was more than one Angus Ban McDonald (not just the one from Muniel, married to Elinor). And indeed, Janet Kennedy's parents were Mary McIntosh and an Angus Ban McDonald (of Loupe).
More difficult will be to determine whether any of my ancestors (i.e. John [UEL] of Hugh of John Mor [of Loupe] of Ruari [Roderick] of Ian, of Neil, etc. married into the Glengarry branch of the family.