Agnes Campbell

Not the daughter of Sir Duncan Campbell of Glenorchy, 1st Baronet and Not the same as Ann 'Agnes' Campbell

The Campbells were *not* Earls of Findlater, not at this time, not earlier, not later, not ever.
Findlater − earldom created for Lords Ogilvy of Deskford in 1638, later superseded by the earldom of Seafield and becoming extinct due to failure of the male line.

Whoever Agnes' father was (and assuming that was her name), he probably was not Sir Duncan Campbell, Bart. She may have been a collateral relative, or the daughter of a follower who had taken the name "Campbell", or have had no connection at all with Campbell of Argyll.