Lucy,
I just came across your post, and I am soory for not reading it earlier. I haven't read through the replies, but thought I may be able to help, because I was once like 'amy'.
I was pg at 14, so you can only imagine wht I used to get up to!

I think this behavior is caused by many things, in my case it was a lack of communication between myself and my parents. But it doesn't sound like this is the case here, sounds more like a situation my DD aunty wne thro.

I think diverting 'Amy's' attention would be a great option. What intersts "amy'? Get her invoved in something, she sounds bored, her energy is being wasted. I'm not sure where her interests lie, but I know if my parents had've gotten me involved in something, and showed some interest towards this interst I may have turned out a little different.

One thing I can say is that new punishments won't work. In fact she will rebel more. My dad tried to ground me once when I was about 12-13, for wagging school... he'd never grounded me before, and it didn't work!

HTH

Tanya