I wouldn't let her go to school. Even if she didn't throw up in the evening, she might not be feeling 100% tomorrow and that could affect the testing.
It's best for her to make up the testing (and I've never heard of a school that didn't have a make up day) when she's feeling better. The results of the testing would be more accurate!
I'll never forget, I ended up taking the standardized testing in grade school when I had a fever. I had felt find in the morning, and was burning up by afternoon.
When the results came back, everything was way above grade level, but my science was 2 grades below! My mom had to convince the school to let me re-take the science because I had gone home sick that day. It took some fighting, but they relented and I came back above grade level (which was consistent with my other testing).
So it's best to just keep her home!