Is the pain in the upper right side of the abdomen??
Is there any yellowish discoloration of the skin or eyes??
And when she vomits, is it greenish in colour??
There are many causes for the pain and hence will need proper history??
She is probably dehydrated because of vomiting, hence her mouth is dry.
Next Steps
Advice her to take small sips of ORS to avoid dehydration
Avoid oily and spicy food
Need to consult online or if her symptoms worsen, to go to the nearest medical facility for proper evaluation