OP, I agree wtih the idea about Girl Scouts or another group activity. I also know a lot of little girls who take marital arts and I've seen the benefits of that in their confidence levels.
It doesn't sound like she is being picked on or anything, just not being sought out. I have been an introvert all my life and I definitely blend into the background pretty easily. Funny, I was just talking about that with my husband and we half-jokingly talked about reading the How To Win Friends book. Best of luck. My heart goes out to you, it is hard to hear your child say no one likes her.
Edited by Hoopin' Mama - 2/11/12 at 7:47am