Dear Doctor , my daughter is 6.5 years old and...

What is the treatment of vomiiting in children ?
you have to avoid dehydration by visiting the specialist  then you'll be prescribed to be given IV Normal saline and IV pramine to stop vomiting and re-check the temprature , if there is fever Acamol Syrup is recommended , as well as your child should eat light food such as soup and other warm drinks , if the cause is bacterial infection then you have to use an antibiotic such as flagyl 
What investigations should be done :
detection of any dehydration signs then stool analysis should be done to detect presence of viral or bacterial infection 
What are the symptoms of Gastroenteritis ?
Vomitting 
Abdominal pain 
Fever 
Advice :
ask for pediatric doctor consultation