To answer the OP's official question, the corps has had 1 female drum major, and that was in 2005.
Melissa was co-drum major with me in 2005, and as Scott said it, she was a backfield conductor until then. Molly was an assistant conductor for me in 2007, and would have have been again in 2008, but was never officially made a drum major. Although, if you ask my opinion, if she would have grown into the leadership role, she would have been fantastic. Far better conductor than I was...but then again, the 3 DMs after me have all been way better conductors too. We were on track to have another female co-drum major in 2009, but it didn't quite work out, and Corey ended up killing it as the leading role.
Melissa had a uniform made that was similar to the traditional DM uni, but with a skirt. It was also similar to the BB uniform, but had a little more BAness to it because of the gun and spurs.