What's your plan? What do you plan to do? How are you at fifteen going to fight your girlfriend's addiction? Addiction is something you fight from within. It's a disease, Peter. You can't love it away. You care and that's beautiful, it really is. But this is her fight. It's her battle and I know it hurts but there are some battles you can't fight for people no matter how badly you want to.
You loving her and supporting her is all you can do and you need to do that while you build your future. She's going to need something normal to rely on because her fight's going to be a hell of a lot harder before it gets better.
She needs doctors, she needs a sponsor, and she needs enough control over her life to give her the courage to always fight.
And I'm sorry about your sister. I'll look into her case, but I know for a fact you dropping out of this won't help her.
You wanna be responsible? Responsible people use this [he points at his temple] even when this [he points to his heart] is breaking. Even when it gets too hard to handle. You have to keep on going.