... and she isn't used to being high at all, I don't think it's too far from the realm of the possible to say that she could have a negative reaction and it could stir up negative imagery from her past.

And I also didn't get that she was 100% better once she puked, she was still stumbling around and struggling big time. She just had a task she was hellbent to accomplish, and the director focused us on that instead of on her POV.