good morning, went through your query.
looks like it is lactose intolerance
get a stool test
done for routine and reducing substances.
untill then hydrate her well with ORS, and start with lactobacillus
sachets 1/2 sachet twice daily dissolved in water. kindly review with reports, if the reports are showing infective picture, we will have to treat the condition or if it is showing lactose intolerance picture, the line of management will change. thank you.