Keep her hydrated with enough fluids and ORS. Priority is always to stop vomiting... as you have not mentioned weight of child I am unable to give doses. If you have an old prescription for vomiting, use that and give only visiting medicine with ORS. Use paracetamol for fever if fever crosses hundred. For diarrhoea use a probiotic like enterogermina vial 1 per day.
Next Steps
Maintain hydration, keep an eye on urine output
Health Tips
Avoid milk and milk products, don’t force feed