Ok, big decision has been made. Since we have a grooms girl, she will be wearing the same dress as the girls but in the color of the boys tuxes. 

Since our theme is something like Victorian/steampunk/fable/renaissance/circus freak fest, our colors are red, black, good and ivory. That mean the groomsmen will be in black suits with deep red accents (tie, vest, etc) and our grooms girl will be the same dress as our bridesmaids but in black and she'll have a red ribbon around her waist. 

My girls will be in deep red dresses with black ribbons (or corsets if they want) around their waists! 

All my planning right now is theoretical of course. No purchases have been made yet but I've only be engaged for like 10 days. I'm just glad I've figured this much out.