Here's how you handle that situation. Rehearse this response, and then feel free to use it (or some variation thereof) ad libitum:
"Okay, nice. It's so great you are well-read. Here's something I hope you can help me clarify. I've read in Stoelting that phenylephrine is primarily a venoconstrictor acting in the vascular beds, and serves mostly to increase pre-load. But, Barash says it has a mixed effect on arterioles and venules, increasing both pre-load AND afterload. Still, Mikhail & Morgan isn't really clear where the primary mechanism of action occurs. Also, none comments about how it's broken down, whether it is through catechol-o-methyltransferase, monoamine oxidase through cellular uptake, some non-specific plasma esterase or some other degradation pathway. Since we use this drug pretty much every day, I'm sure you've thought about this too and have an answer, right?"
Now, you may get all variety of answers from, "I don't know" to "That's not important in the 'real world' when you get out into private practice" to "Are you mocking me?" or even some attempt at a bona fide answer. No matter what she says, your only response should be...
"Oh... I'm surprised to hear you say that."
And, then say nothing else.
You can't approach her now and do this, though. Be patient. Don't seek her out. Wait for a similar situation and then drop this on her. If that doesn't shut her up, nothing will.
Best of luck!
-copro