Being married to a hot-blooded redhead myself, I think I can offer you some sound advise. I'm pretty sure it's *not* about the kilt itself getting dirty, or torn or whatever. It is about you waring "something special" for the wedding, something "virgin". For all us males, a nice kilt with all the assesoires is "special" enough, but I know from experience that some (or many?) woman see it differently - you should wear something that you have never worn before, so everybody will be surprised and awed at your experience. "Look at him in his brand new clothes, bought especially for this occasion, wow!".
My advise: this is a tough one. Maybe you can convince her that adding a new, unused jacket or sporran or such will make it "new" enough?