Chrissy, I'm so sorry. I think all you can do is what you are doing - continue to reinforce boundaries and rules while offering help as you can. She is definitely pushing you to see if you break.
I don't know if this matters in your situation, but I was a really good kid who pushed a lot of boundaries to see if my parents really cared. I guess I thought that if they cared about me they would care what time I came home. Only once when I stayed out all night did I get grounded, and only for one night. I snuck out that night just to test if they would notice and they didn't. My takeaway on that was they didn't care and that I could just do whatever I wanted to do. I guess what I am saying is keep on being firm and letting her know what the rules are and that punishment is consistent and unwavering.
I hope she stops doing this to you.
"Any idiot can face a crisis; it is this day-to-day living that wears you out." -Anton Chekhov