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Please ask you daughter whether she feels like vomiting
if she has food & then there is stomach ache after food ,If this is the situation the she has probably gastritis
(like elders like us have acidity even nowadays children also have).Please stop all out side food ;Whenever she has pain in stomach give her cold
milk she will feel better.Also please consult a Paediatrician(child specialist) who can properly advise some antacids & she should be fine in few days.