My sister is experiencing severe vomiting. it has been going on for almost 2 hours. vomiting every two minutes. should she go to the emergency room?

Depends on severity: Normal healthy people ages 10 to 20 years can get the stomach flu or food poisoning symptoms from time to time. A patient will usually vomit until her stomach is all empty, which is why it is important to NOT eat or drink anything for a few hours afterwards. Then, usual treatment is small amounts of Pedialyte or broth, maybe 1 ounce every half hour while awake. If worrisome symptoms, go to the ER.