Hi, I had gone through your question and understand your concerns. Decreased appetite is common in gastroenteritis , which leads to decrease interest in taking food,give her oral rehydration solution , more liquids .Is she passing urine 4-6 hourly, Is there pain abdomen, Is there blood in stool, is there high fever, is her eyes appear yellow, Is her tummy tight. if baby is well otherwise , active , accepting oral dehydration solution and liquids and some diet ( not interested but taking ) , no large watery stools , no high fever , there is no blood in stool , passing urine every 3-4 hourly , there is no need to worry.You need to worry if there is presence of blood or stools are large and watery .baby is dull or irritable , or passing less urine or having high fever or not at all accepting food and liquid and ORS . She does not need any digestive syrup, appetite will improved gradually.If any of dangerous sign/ symptom present you need to consult your doctor. Gastroenteritis usually takes 3-7 days to improve. Hope this answers your question. If you have additional questions then please do not hesitate in writing to us. Wishing her good health.