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The yellow vomiting
of your 9 yrs old is due to hyperacidity
in her stomach.Ask her whether she feels sensation to vomit before meals and if yes it is due to stress on her body leading to gastritis
.You can give her Ondensetron 4 mg twice a day if she has vomiting sensation and even antacid
like Digene or Gelusil in liquid form.Just in case she does not feel better you have to consult a Paediatrician for examination and treatment.