Thank you for your query,
Nothing to worry as the investigations like ultrasound
, stool, and urine are normal.
This looks like a nonspecific functional pain.
This type of pain around the umbilicus
after eating is common in children and in spite of extensive investigations there will be nothing some times.
But if the pain associated with vomitings, loose stools, night time pain then it is significant.
For pain relief you can give symptomatic treatment as advised by your Pediatrician
Restrict milk to less than 500 ml per day.
And be in follow up with her doctor.
Hope I have answered your query.