Thank you for your query.
is basically a nutritrional issue once other causes have been excluded. It is better to address the nutrition first rather then resorting to medication as the child will get habituated to the medicine.
You may like to see the article on constipation at http://vardaan.net/hl-chfd.php which gives an overview of the actions that you can initiate to control constipation.
I hope I have responded to your query to your satisfaction.
Wishing your daughter all the best.