I feel your pain! I dealt with a child who was chronically constipated for 2 years. First, not to contradict what your doctor is saying but it is NOT normal not to go for a week... not normal for anyone. Here are some things Ive tried (and in combination its worked):
1 - schedule a poop time. My son needs to be directed to the toilet daily...otherwise he is too distracted and doesnt go. When a child doesnt go for a day it becomes compacted. So put her on the toilet with a nice book and have her sit quietly for 5 minutes (no pressure to poop...just sit).
2 - Have her eat mostly high fiber foods (strawberries, oatmeal, flax seeds- I hide that in other foods like oatmeal - beans). My son doesnt even eat white pasta or bread b/c of his tendancy towards constipation.
3 - have her take water breaks and drink at least half a glass before and after school (if she's going to school).
4 - make sure she's exercising for at least 30 minutes a day.
I hope these suggestions work for you. They did wonders for us. Also know that suppositories are not good. They are ok if you use them once every few years but any more usuage is not good for the body.