I also am sending many hugs. As far as her being on her own at 18, in NY State you are responsible for your kid til they are 21. We kicked out our dtr at age 18 but this meant that when she went to DSS for help as far as shelter and food, etc., they called me and said they would take us to court to sue for child support. The loophole was that they said we could have very strict rules she would have to abide by--we could provide the very minimum and have a curfew, etc. for her. Well, when she heard that she decided she definitely didn't want to live at home so then it was her choice to leave rather than us kicking her out. DSS agreed to work with us on how much financial support we would provide for her but we were definitely required to support her.
I am amazed at how little help you seem to have received, I think my county is better. We had our dtr on a PINS and while she violated it blatantly it was a way to document her truancy from school, her not coming home at night, her getting drunk and being hospitalized, etc. Also, we were not the "bad guys"--we told her it was against the law for someone under age 18 to be doing all these things and it was going to catch up with her eventually. And it did-she was arrested and sent to juvie and from there to an Residential Treatment Center (RTC).
I think you have gotten some great advice here, just wanted to point out that in our state we can't just kick a kid out at 18. My dtr is now 20 but lives in another state so we are off the hook but the good citizens of Washington are now responsible for her--she is receiving services there.
Jane