I feel very negatively towards an all girls robotics team. Either it's what I experienced before or whatever, but all girl teams tend to get really clique-y, especially if it the best-friends doing it together. I am happy with a mixed team because it forces you to work with other people and it was really fun because to work with people I never thought I would've. It might have just been the girls on the team too, but it was a bad experience altogether.
Getting more girls on the team, is hard. Really. Everyone is just low on self esteem and when you introduce robotics... it's just a whole new concept that's too hard to grasp. I basically just bug people I know to join
and if they have a good reason not to be on the team, them I leave them alone, but otherwise, they have to give it a chance.