First off... Whatever she does with her life is her decision, and hence not your fault!
Secondly... Some people just take longer to grow up. Some people take longer to decide what they want to do with their lives. She may just need time to think things through, instead of rushing into something she isn't sure about (and having to find a way to pay for it). Everything else is really between her and her parents, her living situation really isn't about you.
Further... The economy is hard right now and college is expensive, it took me a while to find a decent job with a degree from a good school. College may not be the best choice for everyone (although I am glad that I went). I would try asking her what she wants to do and see how that works!
Anyway, I think you sound like a great friend who cares a lot! The above is just my opinion. I hope everything turns out for the best!
Firstly don't blame yourself for the misdeed of your friend. She choose who else see wanted to associate with all this time. What you can do is offer advice, and be there to listen or share thoughts. Show up and insist that she do something, anything as long as she tries to be productive and happy. All you can do is set an example for your friend to see, and point a helping hand in a right direction. You have to be able to help yourself before you can help anyone else. Make her realize this, and that she is important to others so she should be important to herself. Maybe she will wake up and do so.
Honestly, it seems like she's regressed back to being 14-15 rather than being 18.
I mean, that would be great if she woke up, but because of her mom's earlier lifestyle of being in a band like the rock lifestyle consumed her mom's whole life and she kind of lives in it's former glory and is part of another band now and the fact the her mom lived with her grandma until my friend was 8, my friend has no healthy influence to make her realize her soon to be deadbeat lifestyle. Well, except her boyfriend's family who could have a positive influence, I've already talked to her boyfriends mom about my feeling about her future (his mom and I are friends).