I have annoying, insecure, immature friends HELP?

I've grown up with a group of girls (my bf's) and they recently decided to turn on a friend because she lost a lot of weight (looks beautiful) and they've labeled her anorexic! One of them has grown into some "alpha" and she gets this pout or sour look if no one is clinging on every word she says. The group has become increasingly shallow (except for a select few) and it's hard to talk to them about anything else but models and guys. Adults and people in general respect me because of my level of maturity and love of people. Sometimes this sucks because I see what girls do to each other and it's depressing me. I'm usually the one giving advice or a shoulder to cry on but I guess I'm the one needing help this time. What should I do?