I would get in touch with your old pediatrician, explain what it happening with your new and ask her opinion/advice as to what to do. In my opinion, you should change pediatricians. Find one who is more willing to deal with you as an equal in your child's upbringing.
The reason I feel so strongly about this is that we have a child with ADHD and we were advised to put him on Ritalin when he was 2. We refused and finally at the age of 4 put him on medication. As with you, the change is incredible!! He is currently on the highest dose of Concerta (72mg) and has never suffered any side effects. His prescription had to be increased as he grew as well. Our pediatrician has been a God-send...without her we would not have known what to do for him (he was also diagnosed with autism).
I am a big believer in that you know your child better than your pediatrician ever will and they need to respect that. If your old pediatrician can't refer you to a new practice, start shopping around. Try getting in touch with the psychologist who diagnosed your daughter and see who they would refer you to. I hope you find someone you can work with again. We've had so many people look down on us for medicating our son, but until they live our lives, they'll never know, right?
Good luck to you.
B.