It could be that she just can't differentiate between two tartans. Some people are color blind. And some have no eye for pattern. Working in the Scottish Tartans Museum, I encounter this all the time. "Isn't this the Royal Stewart tartan?" says someone looking at an item in the Sutherland clan tartan. "No," I reply, "That's Sutherland." "Well, it looks just like Royal Stewart!"

It could also be that her brother got the wrong tartan!

Once, after a Kirkin' of the Tartans service, I saw an elderly lady dressed in a long tartan hostess skirt, sash, and tam. A little over the top, but she was obvioulsy very proud of her outfit, so I complimented her on how nice she looked. She just grinned from ear to ear. "Do you know what tartan this is?" she asked.

I happened to know, so I told her. "Yes," I said, "I do recognize it, that's the Nova Scotia tartan."

"No," she said, "This is the [her surname] tartan. I bought it when I was in Ontario, they happened to have it in stock in my size."

She looked to proud so wear the tartan, I couldn't bear to burst her bubble. I just smiled and told her, "Well, it looks very similar to the Nova Scotia tartan, and it's lovely on you in any case." It made her day. But I just couldn't bring myself to tell her that a shopkeeper sold her a bill of goods.

I once had a gent come into the museum and asked me to look up his surname. It wasn't related to any clan, so I reccomend a district tartan to him. "I think we are clan MacDonald," he told me. So I looked in another reference, and it didn't mention any clan connection with the name either. But he insisted that he was a MacDonald. I finally showed him on the map where the territorial origin of the name was, and it was on the opposite side of Scotland from MacDonald territory. So I asked him why he thought his name was affiliated with the MacDonalds.

Turns out that the year previous on a trip to Scotland some shopkeeper sold him $600 worth of MacDonald tartan merchandise. :-(

Always pays to do your own research.