I don't love your doctor's response about overreacting - has this happened before? I'd consider another doctor if you don't feel comfortable. Not sure what made you take your kids to the ER - I assume that THEY had symptoms of MRSA (not overreacting) and you didn't just run them in because there was a scare in the area or with other people (could be overreacting).
That said, I don't understand Sadia's response about demanding the ER check the child's pulse. That's not something you need to ask for - it's routine! She obviously had a real problem with her child and doesn't feel she got good advice, and so she is extra vigilant. I agree with her that you should trust your gut, but I'd caution parents about rushing to the ER to check for pulse rate and dehydration unless there is an ongoing problem.
The stress of your ER visit, along with you and your husband's stress level, could have caused a reaction in your daughter. If she had more acid in her stomach from stress and unfamiliar surroundings, and if she had gone without food for a while due to waiting & testing, then putting some hard-to-digest fatty foods in her stomach might have caused the problem. I'm not sure what caused the 2nd night's problem. She could have a little virus going on. not enough for a fever or behavior changes. Try the "BRAT" diet for a few days - bananas, rice, applesauce, toast (or turkey/chicken) but no fat and no dairy, no junk. See if that settles her stomach. Try to increase fluids to replace what she vomited
If it continues, contact the doctor - don't just rush to the ER - the doctor will have her complete records. If you don't like your doctor, switch!
I wouldn't go into a whole thing of eliminating dairy except for the first few days - if she seems to have continued problems with this, email me back and I can help you nutritionally to get her body in balance. (No charge!)