Please help me figure this post out. From what I can tell you want to understand "emo people"?
Well, you can't understand them. There is no such thing as "emo people."
Insecure people, especially in junior high, search for a definition of themselves and try to fit themselves into that box because they feel like if they were honest about themselves to other people, they would be rejected. (Now, obviously, this isn't a conscious choice, it's a subconscious one.) "Emo" is one of those boxes. By their definition, an "emo person" must look, act, and believe a certain way, listen to a certain kind of music, and be around the right people.
There are other stereotypes also. You can probably think of some.
The assignment of "roles" is completely arbitrary, and stems from a growing collective insecurity. In junior high, people are either afraid to be who they really are, or maybe haven't decided who they are yet. None of these definitions or stereotypes truly exist except in the minds of people who look for such things.
My advice to you, if you are trying to find a way to fit in, is this:
Don't limit yourself to one stereotype or another. Be who God wants you to be, and who you want to be.
Be honest with yourself-- pick the music you listen to on the basis of whether or not you enjoy it, not on the basis of what other people think you should be listening to.
Don't dress a certain way because you feel like you have to, or because you want to promote a certain image of yourself, but dress however you want.
And don't let anybody bother you on account of your Christianity. That's not up for them to decide.
Basically, if there's something you have an interest in, pursue it. Don't try to fit in, because it will only bring anguish. I've been there.
You WERE wanting advice, right? I couldn't really tell...
And about that girl that cuts herself: if you think she was serious, tell somebody right away, because she needs help. People have died from hurting themselves.