(Any doctors or nurses on here?) what caused her stomach pains?

Hey guys i hope everyone had a great NYE!
Last night my friend had too much to drink and so as the good friend that i am i went with her to the toilet everytime she had to vomit. But i noticed several times while she was throwing up that her eyes were rolling and she was screaming in pain "my stomach hurts so muchhh!"
So i was very worried that something was seriously wrong.
Can somebody tell me what might have caused that pain in her stomach?
(Any doctors or nurses on here?) what caused her stomach pains?
Post Opinion