Stress in Friendship

I seem to have that. All of my friends are pretending to be something they're not. For example, one is doing drugs and partying all the time just to have friends. I know this because one day when she was upset, she told me. Those friends don't really even like her for her. Just her drugs. She always seems to choose them over me, when I try my hardest to be the best friend that I can, but apparently it's only one sided. I don't have many good friends, so I don't want to lose her, but apparently, I'm starting to have no choice. I don't know her anymore, and shes changing too fast for me to adjust.
So, once again I am conflicted. She's a terrible friend, but I can't seem to just let her go down that path, even if I know I should.
Then there's my other friend who tries to grow up too fast. And it seems she's getting to the point where I can't catch up... Yet again. She tries to seperate herself by dying her hair black and rebelling against her mom- who may I mention is probably the most lovely woman I've ever met.- and I think she has an eating disorder? Her pants size is 0, and she complains about a bit of 'flub' which she apparently has on her stomach (which, by the way, is skin). She rarely eats anything, and she sleeps very little. If you tell her to do something, she'll automatically do the opposite. Some of the things she's done, you'd swear she had a death wish.. She's probably the most beautiful girls I know, and she obviously doesn't see it at all. It worries me, because I don't know where shes heading with her life.
Those are just two of my stress provoking friends, and I have about two more. One lies about her life to everyone including her friends, and dates boys over the internet, as well as 'sexts' and such. Do I have to mention that she's fourteen?
My other friend is a lot like the second one, but not as alternative, and more.. fake about things, I suppose.

I should probably stop letting their problems rule my life but it's difficult, as some of you may be able to relate.
Anyways, I just wanted to get that off my chest. That's all I have to say for this entry.