The foul odor in her breath is likely to be due to improper oral hygiene. I would suggest brushing teeth twice daily. Brushing at night is very essential. You also need to teach her the right technique. The direction of movement of the brush should be gum downward. Your child could indeed be suffering from a gastrointestinal infection which may be the cause of vomiting and foul smelling stools. The overgrowth of anaerobic organisms in the bowels could be responsible for the foul odor in stool. Give your child plenty of curd or yogurt since it contains beneficial bacteria. You may give decolic to relieve the stomach cramps and some antiemetic if she has vomiting. Maintain proper hydration by giving ORS (oral rehydration solution) prepared by mixing a full sachet in a litre of plain water. Antibiotics may be required but I would insist that you visit a doctor so that he would be able to assess if antibiotics need to be prescribed.