Suggest Treatment For Stomach Pain, Diarrhoea And Vomiting

Hi Doctor, My daughter is 15- nine days ago she had an episode of vomiting and diarrhea (together)--she vomited twice and had diarrhea with it--leading up to it she was complaining of stomach pain. After this was done, she felt fine. The very same thing happened six days later. Early this morning, she woke up with sharp upper stomach pains-after approximately 45 minutes she had diarrhea (no vomiting this time)--the pain lasted after the diarrhea (two episodes) and then she was fine--she is eating as usual again. I brought her to the doc and he ordered an ultrasound (to be done next week)--he said she should go to the ER if it happens again so she can be checked while symptomatic. My daughter had a little pain today on the left side of her abdomen but nothing else since the diarrhea. Overall, she said her pains tend to be high (under the breastbone). Any thoughts?