There's lot of girls out there waiting for groups and hoping for friends to express an interest. I wish I could help but apparently I just don't know enough people to make all this happen! I don't need to prove it - have you seen how often I do photo shoots alone?
Here's how I feel about this...
People are shy. People also like to have fun. If you go ahead and do a shoot alone, once your friends see they'll want to join in too. It might take a while but you'll start adding group members and the fun will grow. Until then you have an opportunity to become more comfortable in front of the camera by yourself. It's actually a great opportunity because when girls do join your group they'll look to you for direction and encouragement.
Make the most of it. Have fun and take great pictures. You'll entice your friends into your group and they'll wonder why they didn't join in sooner!
Being in a group by yourself isn't so bad. That's why we started our random Self Portrait Friday.