I know it's not going to happen, but I wish so much that Carol is just proven wrong. Yes, it is perfectly possible for her to not know of a medicine that uses that plant. Yes, it is perfectly possible that the assistant was just upset that Carol was acting high and mighty in her opinion. I want Carol to be proven wrong.
I also want Carol to grow as a result. She doesn't need to have her confidence shattered. She can take it as a learning opportunity, a chance to accept that she doesn't know everything but that she can still have faith in herself. Having faith in yourself doesn't mean that you have to go with every suspicion you have of someone else. Oh no, the assistant smirked!?!? She must be evil! That's crap.
Too bad none of that is going to happen and the assistant is going to turn out evil. Too bad.