my 2 cents worth... i agree with the posts that say talk to her. ask about the problem. i would emphasize the cultural identity. a kilt is a historical garment (i know, preaching to the choir) from a culture of pride and "manliness". my wife drools over sean connery - even in a kilt. the times i've had to defend my kilt i've related it to the person doing the asking and their culture.

i don't think i'm phrasing this well... i live in cherokee country. i'm part cherokee myself. folks in this country do not poke fun at cherokee attire. if they poke fun at me i ask if they'd like me to ridicule their cowboy hat or ribbon shirt. my culture is mixed, but the scottish aspect means as much as any other. referencing their pride in their culture seems to help. fwiw.