I don't know that there's an etiquette question seeing someone else in the same office; I'd just be mortally uncomfortable doing so right away :-)

I think I would have had to jump up and act all anxious and paranoid or something and yell, "You mean you don't know this stuff?! You mean I have to decide whether or not I have the correct symptoms?" and whipped out my bulb of garlic or something to ward her off.

That sounds/is very disappointing though :-( Definately sounds like she wasn't too comfortable with just being a person, herself, like she was trying to "impress" you or something. Don't know what I'd do.

Did you have a couple more people to interview that aren't in her office? I'd maybe come back to that office "last" if you have any others that aren't in that office that might work to interview first.