I hope she is feeling better since you wrote this. I think she might have a stomach bug. Those things come along despite our best efforts.
She wouldn't have the flu that you got her vaccinated for - influenza A and B or H1N1 don't produce stomach issues.
If she can't get at least an ounce down every 15 minutes of water or pedialyte or Gatorade, throwing it up a lot, you might need to get her to the ER. The last thing you want is for her to become dehydrated. Then she'll end up needing IV fluids and that is really unpleasant. But it's better than her heart being affected, because you have to be careful about dehydration hurting the heart. (The ER doctors told me about that when this happened to my own son. They were grateful to me that I worked so hard to get that one ounce every 15 minutes in him, though he couldn't keep it down.)
The other thing you can do is to get rectal suppositories from the pharmacy to help her with fever. If she starts throwing up so much that she cannot keep down the motrin or tylenol, this works to help get her fever down.
Good luck, and I hope this passes quickly!
Dawn