foster care and medication

I am in the midst of adopting a 9 year old. for safety's sake, i'll call her Abeni. She has been in foster care for 5 years. She has had 9 placements (including family placements before foster care). Before foster care, she has always been pretty wild in school...but her birthmother had no consistant housing, nor job, and Abeni was the caregiver for her younger brother and sister. She has been on Concerta, for ADHD, for the longest period of time. In a previous placement, they realized that she had doctors orders to take Zyprexa instead of a medication that was supposed to help her sleep. They started her on Zyprexa, but took her off when she started gaining weight really quickly. This is around the same time when she first met me. It was also shortly (2 weeks) after moving out of the home that she had been in for 2 years. Several weeks later, she had figured out that i was a potential adoptive mom, on her own. She started rebelling at school...and then at home...to the pont in which she fought and hurt the foster mom's bio-child. she was telling everyone that she was going to my house anyway, and she didnt have to listen to anyone. When the bio-child was hurt, she had to go, and no one would take her, because she wouldn't calm down. They took her to a children's residential treatment center, where she immediately calmed down, to the point that they question why she was there. they started her on the Concerta, again, as well as Risperdal, and Welbutrin. The Risperdal had been prescribed the day before she erupted, and in the state she was in, she was refusing to take any pills. They added the Wellbutrin, but commented "We see that there is definite anxiety, but i don't know if she is really ADHD". And they had a point, when scared, or in a new situation, she is the ultimate calm observer. Its when she relaxes, that she gets a little wild...even w/medication. it almost seems like she watches to see where the limits are, and then when she has them down pat, she tests them all at once. Now, Abeni says she doesn't even know why she had to go to the hospital. She has no memory of the incident. I can't figure out if she's lying, or really has no memory. She has been doing fine on the Converta, Risperdal, and Welbutrin, but i worry about the impact of all those drugs on a young mind... especially when i've read that children going through multiple moves (even within the same family) often exhibit the same signs as ADHD. However, I've also heard that that specific combination of drugs has had a good affect on adult ADHD. Once adopted, i'd like to wean her off of all of these meds...or at least down to one. but i don't even know if that will be possible. how can doctors make medical diagnoses w/o seeing the chilld off of drugs? -Laini