From your description of your daughter's symptoms and the fact that she seems to be otherwise growing well, it is likely that her symptoms are related a 'sensitive' gut.
She probably has a decreased transit time, meaning that her intestines empty out more rapidly than normal.
This leads to a lack of absorption of the bile that is normally re-absorbed by the large intestine, leading to green colored stools.
The other symptoms seem to indicate that she may be developing an Irritable bowel syndrome like picture.
There may be a component of gastritis / reflux given the pain in the epigastric (above the belly button ) area.
I would recommend a trial of antacid medicines like Prilosec/ Lansaprazole under doctor's supervision, and a diet completely devoid of any junk food / or food containing large amounts of preservatives for at least the next couple of months
Giving her plenty of fruits and salads, and possibly a trial of Imodium may help in relief of the present symptoms
For more information on children with IBS, read herehttp://digestive.niddk.nih.gov/ddiseases/pubs/ibschildren/
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