And the other problem is that most of what you have tried really doesn't work for a child this young (in a few more years, yes), and it definitely doesn't work with ADHD kids. If you were to go on the ADHD site where I usually post, you would see this is pretty normal behavior. The sad thing is that whoever diagnosed her didn't give you much info on how to work with kids like her.
I recommend the book, "The ADD/ ADHD Answer book," by Susan Ashley a lot. I think in your case I would highly recommend it because it will cover everything from discipline to coping with schools and homework to IEP's , etc.
Another book which is very age appropriate is "SOS Help for Parents," by Lynn Clark. She explains how to use the timeout system effectively. This system will also work well for ADHD kids - as long as you understand what ADHD is doing to the child.
If you do have any more questions, you can always find me here -
http://www.medhelp.org/forums/ADD---ADHD/show/175
Best wishes!