What Causes Child To Have Vomiting Sensation And Weakness?

My 4yr oldChild was at the rodeo 1pm to 7pm had bubbles of pizza cotton candy and fries..She is vomiting now or attempting to w very little result...initial vomit was of weird consistency..now the lil that does come up looks like flem and bile.. been goin on since about 3am and now its 5am. When she needs to vomit she doesnt want to stand n get limp.. Is it because shes worn herself out physically or smthn more is my concern.. shes responsive..tries to doze off..I ask her to sit up n sip water she does..communicative but sleepy.