L.W.
It seems youve done everything you need to do.. dont over dramatize it it could just be a first. or maybe she is looking to do "something naughty" . Sometime kids that are really good need to do somehting bad. The next time the cops and court wont be so easy on her. ( i am geusing she got a way with it?)
Just keep the lines of communication open an let her know your there for her but if there is a next time, she will have to fend for herself ..
good luck with this. its tuff.