How Can Strep Throat, Stomach Pain And Vomiting Be Treated?

My daughter has strep throast and is complaining loudly that her stomach hurts. She has vomited several times today and I am concerned that she cannot keep her amoxicillin pills down long enough for them to do any good. I have tried ginger ale and saltine crackers and threatened to take her to the emergency room to have a phenergan suppository inserted but nothing seems to be making the nausea any better. She is 24 so the emergency room threat was supposed to make her sit up and convince herself she was feeling better. Any other suggestions?