I have also heard for some mental illness' that a very structured but simple daily routine is good. Always go to bed at the same time, etc. It helps me greatly when I keep the same routine.
I have been told that there are many foods and dyes in food that can cause this. And I have heard accounts of people going with an 'all natural diet' and had amazing results. This is all I can tell you, no specifics. Good luck with your daughter.
My step grand son has ADHD and he is behind too...