3year old might have eaten poop. what can happen?

Hello and welcome to e health forum.

The most likely result with such a incident would be a gastrointestinal infection resulting in diarrhea, vomiting, fever, reduced appetite, etc which may necessitate treatment with oral antibiotics and rehydration therapy.

Other possible results may include chronic intestinal parasitic infestation , with parasites like tapeworms, roundworms, etc.

You may watchout for abnormal signs and symptoms in your daughter, and consult your pediatrician for proper help and advice.

i hope this helps.