<human>: Can you give me the gist of the text in a nutshell?

A girl I love deeply has been getting into drugs and other bad shit for the last year (basically spiraling out of control). For a while she completely stopped talking to me (for months) because she said she knew how much it hurt me to worry about her. Her and I started talking again about a month ago, but she ignores me a lot and still does these stupid things.

 I love her, but I know she'll never love me back, nor will I be able to help/"save" her. So I just want to forget her. But I can't. The littlest thing will remind me of her and then I'll start having massive anxiety thinking about all the trouble she could be in. I've been trying to help her for so long, but I can't. I don't know what to to. If she'd let me be there for her, it'd be different. But I'm pretty much destroying myself worrying about someone who doesn't even think about me. What do I do? I feel so hopeless. I feel like I'm going to end up wasting my 20's by drowning myself in this. Please don't think I'm an asshole for "giving up", because I'd never give up on her, I just don't want to hurt anymore when there's nothing she'll let me do.

I hope this is the right place to ask such a question, I'm sorry if it isn't (could someone direct me to a better place to ask for advice about this, if not?)
<bot>: I'm drowning in anxiety over someone I can't help (but deeply care about), and I don't know what to do.