Trapped in the middle- of SIX warring friends!

I have six very special friends. They're all virtual ones, and only two of them live in America, in fact. They're all fighting with one or more of the others, as well.

N, age 17, just split up with L, age 15. N called L a sl*t in a fit of rage, and she's been really nasty to him in retaliation. Since I'm a really friendly person, N came to me to talk his problems over. I told him he was right to be mad at L for being such a horrible ex.

However, behind the scenes, L has been going on about how N is so horrible. L and N are both dear friends of mine, and I've been trying to mediate the conflict. I really have no clue what to do from here.

M, age 16, is the elder sister I never had. Our friendship is perfect, and has been for the year and four months we've known each other. A, age 14, is also very dear to me, and is an incredible help in my work.

M and A dislike each other intensely. Well, it's more M doesn't like A for some reason (I think it has to do with immaturity) and A fights back by making snide comments about her. (I'm pretty sure A is also terrified of her, but she'd never admit it, even to me.) It doesn't help that M has a ton on her plate. I'm one of the few people she doesn't snap at.

D, age nineteen, and H, age eleven, are polar opposites. D is a college student from the Balkan area (I can't be more specific) and H is a extremely excitable homeschooled Irish dancer and American Girl fan. They both really like me (D is the closest I've ever had to a brother, and H considers herself my little sister, which I agree with) but despise each other. They're incredibly different, and wouldn't acknowledge each others' existence (apart from D's occasional expression of his wish to strangle H) if it weren't for me.
M also doesn't like H much, H and A are a little wary of each other, M and D are e-dating, A and L are friends, D is L's e-brother, L and M are friendly towards each other, and A has an (secret) e-crush on D.

What should I do with L, N, A, M, D, and H? I'm confused and upset and ready to scream at them and tear my hair out. Please help! I'm at the end of my rope here.