Puppy Sick/Not eating?

We got our boxer mix on friday from the shelter. Before we left, the dog warden gave her her 2nd round of shots, a flea pill, and a dewormer. She was fine on Friday, and we took a 2 1/2 hour trip for my fiance to meet my parents. The next day on the way up she started to throw up. It was white and foamy. And she's been doing that through today (Monday). Is she having a reaction to the shots/dewormer, or does it sound more serious?? And she is drinking, but not eating. I'm so worried about her.. we've only had her for three whole days and we're already in love with her!