this Isabel was actually Elizabeth Isabel stewart that married Archibald Campbell, 2nd Earl of Argyll. John Stewart 2nd earl of Lorn only had by wife #1 three daughters married to Campbells of Argyll, Glenorchy, and Ottar. (see https://www.stewartsociety.org/history-of-the-stewarts.cfm?section=...) The Lady Elizabeth Isabel Stewart was the Daughter of Sir John Earl of Lennox (see https://www.stewartsociety.org/history-of-the-stewarts.cfm?section=...) The Isabel Stewart that married Colin Campbell ancesters to the Earls of Argyl was the daughter of King Robert III of Scotland and Annabell Drummond.(see https://www.stewartsociety.org/history-of-the-stewarts.cfm?section=...)