[33girl]

Since mixers aren't mandatory, and it sounds like a lot of the girls don't want to go, I would not schedule it. If you do plan it and no one shows up it will make your sorority look REALLY bad.

It sounds like a lot of the sisters don't feel comfy around the brothers - maybe ask them to come with you sometime when you are just hanging out at the fraternity or introduce them at the bars and such. I know it is totally annoying when people want to party with the same old, same old, but it's a lot worse to plan a mixer and not have enough sisters there.