Sounds to me like she was trying to pay you a compliment without being able to come up with the actual name of the garment you were wearing. As some others have stated it is so rare for most people to actually see a kilt being worn outside of a Saint Patrick's Day parade that they simply can't think of the correct word to use. It certainly doesn't sound like she made the comment with any ill intent.

The comment from the lady behind (Then the woman behind me tapped me on the shoulder and said, "Even though Englishmen have died for less, try not to kill her, lad.") you was priceless.