Worried as f*** about my friends, and I want to help, but I don't know HOW!!!

AW is depressed, has an eating disorder, her blood doesn't clot properly, and most of her friends leave her in the end, I'm the only one she hasn't been mean to yet, and though I don't think she will, I'm still hopefully prepared.
She's mostly fallen out with my other three main friends, though they still talk to her occasionally..
And her mum's a gambler, and I THINK she might smoke...
UPDATE: AW smokes AND drinks, and might possible be pregnant, she's hooked up with a couple exes and things went further than she wanted

My sister smokes, and she lives at home, not 18 yet, and f*** no, I ain't telling Mum that, I don't want her to get in deep s***, and, though I don't see her much, I still feel like I SHOULD do something!!

BW does SO much, I'm surprised she hasn't dropped dead from stress yet, and I'm not kidding! She's walked into a few classes just crying from stress! She also clinically depressed, and is in a few choirs, does singing and dance at/after school, AND somehow gets all her (home)work done, usually really high marks, and she's a bit ahead in maths almost every period, and does more work than anyone else, and she still talks to people during the maths period...
Yet she's not good enough for her parents. They never praise her, or do ANYTHING to show they're proud. She's not perfect enough for them... Yet I'm really proud of her, though worried, I really think she should do less, and relax more...

KT (no her name's not Katie) I'm most worried about... She has depression, a sleeping disorder, and eating disorder, she used to cut (her current bf made her promise to stop) she hates her home life, her (step)siblings, and almost as soon as she's home from school, her mum/step-dad leave and get her to look after her siblings. Her step-dad rapes her, and on 20/10 she told me her monthly was 2 weeks late. Her mum's tubes are tied, so how would her mum react if she found condoms in the house? So her step-dad doesn't use anything.. And she's not even 15 yet!!
I can guess that her step-dad would just say, If KT was pregnant, that she's probably been screwing her bf, even though the farthest they've gone is a basic (I think) k***
UPDATE: Her monthly came today, 3 weeks later than it apparently should have.... f*** I was worried though, and so was she, and Hell, I'm glad....
Update again: furthest is now a make-out, she says. But I won't update this any further


Every time a friend has a problem, I feel like I need to do something, but with these three, I feel like.... like I'm SUPPOSED to do something to help, to improve it at least a BIT!

I don't know KT's exact address, but I want to go to the cops. She probably hasn't cos she doesn't want to make a fuss, or she's too scared of what her step-dad would do, I think...

The school probably has her address, so when I have to catch the early bus to school (twice a week), I'd have time to stop off at the cop station and see if it's open, and tell them about her+her step-dad, but also if they ask for her address, tell them the school probably knows, then give them her full name, class+the school....

Should I go to the cops?? If anyone bothers reading this at all, should I go to the cops for her?
UPDATE: KT says she told her Mum after every time, and that she's starting to believe her, and that her stepdad's moving out soon... But I kinda want to go just to give less chance of that happening to someone else...

And if anyone has bothered reading this, I might also point out I've never been one to express feeling much towards people, tell them I love them, or express any someone depressing emotions, so you don't really need to give an idea if you have one, involving that type of thing...

God, I've been typing this for like, 40 minutes!