I believe she means everything happens for a reason. Vomiting is not a bad thing. Like our friend said, it smells bad, tastes bad, feels bad, but afterwards, we feel much better because what was making us sick is out of our body. I could get all the examples dairyfreelife gave us and explain you why they happen, but my English isn't good enough when it comes to reactions and body parts (and complicated names, and everything else :P )
Oh, I remember something now that may help you to realize that humans didn't learn how to vomit. I learned it in Biology a few weeks ago:
Exocytosis: When a cell directs the contents of secretory vesicles out of the cell membrane.
Take a look at the picture and tell me what it remembers you:
http://kenpitts.net/bio/images/exocytosis.gif
I know it's not much of a point, but see, even our cells get rid of what they don't need somehow.
However, I think that if you want us to understand you, I'd love to see the link from where you've learned that vomit is something we learn.