Your discretion is admirable. I've never had this situation and I live in Rochester, NY - close to southern Ontario & thick with Scots. However, I'd like to ask these individuals, "Then, you are familiar with Wilson's Key Pattern Book? Logan's Thread Counts? The initial Government Regimentals and their numbering? The Industrial Revolution & George IV's visit? Sir Walter Scott and Romanticism? The existence of "District" tartans eventually co-opted as "Clan" tartan? The repeal of 1782? etc., etc., etc.,...just to see what they might say.

Anyway, considering the circumstances surrounding this encounter, I will apologize to you for her.
Slainte