Notify the Teacher... perhaps, these girls are "known" for being mean. Sure they are "just kids." BUT, at this age in school, it is simply "mean" when other kids are indeed "mean" to others. There is no excuse for that. I WOULD, teach your daughter all about "character." The difference between "mean" and "nice." Do NOT TELL HER that "kids are just kids... so suck it up" kind of thing. (ie: being a 'victim').
Instead, she CAN be taught, that you understand her feelings and that she CAN ask for help or just commiserate with you. This is so important for a little girl.
Next: for any child, there is something called an "external locus of control" or "internal locus of control."
In External Locus of Control the Individual basically believes that his/her behaviour is guided by fate, luck, or other external circumstances. In other words, they are just a "victim" of whatever happens to them.
In Internal Locus of Control, however, the
Individual believes that his/her behaviour is guided by his/her personal decisions and efforts. In other words, that THEY themselves, decides AND determines what kind of life/attitude/outcome/wish/hope they can attain.... because it is up to them. They are not a "victim."
These concepts are important... for any child/adult. Because it affects their personality and how they feel or view "life."
To me, "self confidence" is not the same thing as "Self-IMAGE." Or, about doing something to someone or just putting "on" something in which to make a person feel more confident. RATHER, it is about 'teaching' a child HOW THEY CAN PROBLEM SOLVE and cope... with something. To get creative about things, and looking outside the box. To know that OTHER people CANNOT "make" you feel like a "loser" but that its how you feel about yourself. No matter what.
So, those kids are mean. They judge your girl according to her looks. So what. Yes, its 'rejection' to your daughter. BUT... gradually show your girl how SHE can gear her attitude about it, differently.
ie: we all know "people pleasers" or people who just do their own thing, despite- Because they don't base their self-image on what OTHER people think of them.
Find what your daughter enjoys or is really good at. NURTURE that. Have her create a self-image for herself that is "happy" and that she loves in herself. How does she think of herself? Positively or not? If not why?
The thing is, don't push her into things, unless SHE enjoys it or is interested in it. "Sports" does not build self-confidence for all kids. Perhaps your girl likes art better? Find what SHE likes to do, or is good at. Then, THAT IS THE KEY to "allowing" her to blossom, and find herself.
When mean girls 'reject' my daughter... she comes home and tells me. I don't judge her. I just ask her things, non-critically like: "Oh, what did you think of that? How did it make you feel? Are you okay about it or not? What did you do instead? Do you think they were genuinely mean or just not your type of friend anyway?"..... so, in the process, my daughter will understand how she feels and she will always say "I am always myself... they don't bug me, I play with who I want to...."
Instead of choosing something "for" her to boost her confidence.... (ie: you mentioned you need to find something quick so that she is not sad all the time). I would let HER choose something.
Or simply teach her how to "problem solve." ie: converse with her: "if a kid is mean to you or rejects you, what can you do instead? (a) be sad (b) go away (c) find another friend (d) be mad (e) realize that you don't need them to be happy. (f) find other friends who are like you and are nicer. (g) make your OWN friends. Etc.
Sorry for rambling, just some ideas. For a child to be "confident", they have to find themselves and KNOW and LOVE Themselves, and be PROUD of themselves, and be able to nurture their OWN talents/interests too... and understanding how THEY can "change" a situation for the better, or just letting others "control" them. (ie: external locus of control).
No Mom likes seeing their child 'rejected." But, even "self confident" children/adults have a hard time accepting 'rejection' at times, and we all get hurt feelings. But its how to cope.
All the best,
Susan