What to expect from a Neuropsych eval?

I have read on these forums for years that getting a Neuropysch evaluation for our kiddo's is a good idea. Last year a psychiatrist (family friend) told me that getting a NeuroPsych eval on the Queen would be the next step. Last August the appointment finally came for the 6-8 hour evaluation. Thirty minutes into the evaluation, the Queen just lost it. Behavior was off the charts and large objects (full bottles of water, etc) were being thrown at the doctor & I. So, the doctor hospitalized her and said she can't evaluate her until she calms down. The neuropsych had me come back last October (without the Queen) to talk. We decided it would be good to wait until the summer of 2014 to evaluate her because my daughter had so many psych & school evaluations last fall. I contacted the NeuroPsych recently to set up an appointment for this summer explaining that the Queen is much calmer now. Her comeback was, "If she is so calm now, why do I need to see her?" I am at a loss. She can't evaluate her when behavior is off the charts or when she is calm. I don't know what to expect from a Neuropsych evaluation or what to ask her. After a few email exchanges, the Neuropsych has agreed to meet with me this Thursday. My daughter is 6. She was heavily drug exposed in-utero (meth, heroine, cocaine, etc) Her behavior has been off the charts at times. She is on a regimen of medication (Risperdal, Ritalin, Trileptal, and Prozac). I am not a fan of the risperdal but okay with the others. I do now know what to ask or what an evaluation from this type of physician can do for my daughter. Any feedback is greatly appreciated. Thank you!