I think that laying down the law will not teach her anything. Guiding her to start thinking about her future and what she wants to do with it is the better way. She may have never been exposed to learning to organize, prioritize, and planning. She may have never been given opportunities to have choices and have consequences she understood as part of that.
I know there was no way when I was 18 that I could have told you more about life other than I work and make money to spend on clothes and stuff. My parents take me places if I need to go or I ride the bus....I had no usable life experiences to fall back on or no real maturity to live on my own. I probably would have starved to death and not understood that going to the store then cooking a meal was what I needed to do. I would have eaten out until I ran out of money.
I understand her mentality. She needs to learn how to live and make choices. It's on you now to teach her.
Laying down the law is only going to reinforce that adults are mean and won't let you have a childhood. Even though she is 18 she still feels like a teenager and not an adult ready to go out into the world.
Perhaps the college she was going to was too hard. I went to a junior college and thrived in the atmosphere, nearly all straight "A"'s. I got a full scholarship to OU and moved to Norman expecting college there to be a continuation of jr. college. I hated every minute I was there.
I was in a humanities or history class and there were over 300 students in it. The professor came out on the stage of the auditorium and announced the grading curve, how many would make an "A", a "B", and so forth. He told us if everyone made the same grade he would put everyone's name in a box and draw them out and assign whatever grade he felt like.
I had a communications class and I was one of two ladies in it. The rest of the class was the football team. The professor propositioned me. It was not fun to be there.
I transferred to Stillwater and enrolled at OSU and the moment I sent over the hill on highway 51 where you can see the whole valley I felt like I had gone through the veil. I knew I had come home to where I was going to live the rest of my life. I thrived in the classes I took there.
The point is, the classes, the attitudes, the people you sit beside, the mood of the campus, it all contributes to the college experience. Perhaps if they can live at home next fall both girls can go to college and ride together. They might even have a couple of general ed classes together and the can help each other to learn how to be a studious student.
She needs to learn, not be ordered about, she needs to have support, not a smothering blanket, she needs you to help her grow and not be punished for the experiences she has lived up to this point.
Otherwise there are the options of joined the military, going to a work program like the job corp. She will learn job skills and learn to be an adult in those type of lifestyles. If she truly does not want to go to a traditional college there is always vo-tech or some other kind of technical programs like University of Phoenix.
If her parents are claiming her on their taxes they need to stop. She is an adult that is not living in their home and she needs to file taxes on her own behalf, so she can establish she is an adult applying for financial aid and not a child living at home with wealthy parents who can afford to send her.