Make sure your daughter is drinking half her weight in ounces of water every day. (so if she weighs 50 pounds, she needs to drink 25 ounces of water/day.) Most kids (and adults) are severely dehydrated. When I say drink water, that means water; not milk, not juice, not soda pop, no tea or energy drinks.
My daughter when she was 6 became so constipated that she had to have a colonics done (she battled with constipation and encopresis from babyhood up until we changed our diet). You don't want to let it get to that point. She used a lot of Miralax when she was little (which if I had known then what I know now--that it has a lot of plastic in it--I would have never given it to her) as well as laxatives. Again, NOT the correct thing to do; the correct thing to do is to take out inflammatory foods/foods that cause constipation (cow dairy is a BIG culprit) and incorporate foods that help eliminate; that would be veges and fruit because of their soluble/insoluble fiber (but watch the fruit; fruit is high on the glycemic index, and parents need to watch their children's total intake of sugar. Diabetes is now a national issue, and more and more children are getting it).
In my daughter's case, it all stemmed from her Sensory Processing Disorder issues and a gluten and soy intolerance; we also took her off dairy and started eating organic with lots and lots of veges. The dietary changes were what helped finally to get her regular; she goes BM almost every day now and rarely ever goes 2 days without going (she is now 15 years old).