How can I help my child gain more confidence? At school? At home? New environments?

My child is a sensitive child. She is 6 yrs. old. We have taught her to play fair, manners, and how to be respectful of others. She has such great leadership qualities, but I don't have the answers to help her when there are problems with friends. She feels like she plays fair with her friends. She says she follows their rules when they choose a game, but when it is her turn to choose the game, the girls runaway or speak over her. I have witnessed this. She has such a sweet personality. She has some close girls that she talks about in her clroom, but this happens when all the girls come together at recess. She says she doesn't want to tell because she thinks that is tattling. But, I am terrified of people running over her b/c of her sweet personality. I have seen girls in her preschool hit her. My personality is not like hers. I much more outspoken and I just want her to take up for herself. But she is so sweet she says we will just pray for them. I am so scared of her teenage years of boys taking advantage or girls peer pressuring her. She wants to please everyone. I need some advice. I want my baby to be strong when I am not with her and I want her to continue to talk to me like she is now. Her confidence is becoming stronger. She will now walk up to children and ask if she can play, but I have witnessed and she has told me that some kids tell her no. But mainly it is when she tries to talk to older kids. I love her. It just breaks my heart when I hear this from her.