I feel for you! I'm a high school teacher and deal with 180 teenage darlings every day
I don't have any solutions for the curfew problem, other than rewarding her with something if she manages to come home on time for 2 weeks (and then reward for longer stretches)
I would cancel her cell phone number or make her purchase a track phone where she has to prepay her own minutes.
Best of luck - I have found that keeping a good sense of humor helps me keep my sanity!