St. Andrews day on Monday now the underwear question?

It depends on how she sees herself and her ancestry to the notion of the kilt. One way of looking at it would be, if she is going to wear a real kilt that would be proper on a gent, then she should go as a guy, and be regimental in all it's glory.

If she wears a kilt skirt, the ones made for a lady, typically higher off the knee or at least lighter than the seven to nine yarder woolen kilt for a gent, then panties might be better suited, especially if a good gust of wind should come up.

I once went to a highland festival where a girl wore a mini-kilt skirt with no underwear. She was a hit when she got to dancing, but she was dressed sexy toe to heel, there was a lot of beer, and the music was really rocking so the environment was just right. At work that might not be a good idea.

Lady underwear is acceptable in my opinion..