I agree (along with everyone else it seems) with the fact that she's trying to control you.

Bottom line... SHE has issues with her OWN self confidence. So much so, in fact, that she worries about what people will think of HER when she's with OTHERS. I suspect that this isn't her ONLY "issue" to deal with, so you're probably better nipping this one in the bud.

Also... I think that wearing a kilt (or on broader terms, going against the mainstream social grain in some respectful way) IS a test of friends' character. If the person REALLY cares for YOU as an individual, they will accept your decision to wear the kilt. They may not be HAPPY with it, but they'll at least accept it. If they really cry, whine and moan about it and refuse to go out in public, it's indicitive of a larger issue within either the friendship or the other individual.

Think of it as a "good way to weed out the people I WOULDN'T want to be friends with ANYWAY". Who needs people that are only going to be negative aspects in your life? Life is too short to live an unhappy existence.