Some kind of deer in the headlights syndrome?
I guess it must be a similar situation as to when Jahova's witnesses actually get invited into someone's house. They'd be like "Um.. uh... I'm sure I memorised something about Jesus, but blow me if I can remember what it was" - lol

OK - for real now-
Say something like:
"So - I didn't get to find out anything about you the other night, and my buddy didn't tell me much either. What's your name, what's your sign and what's your shoe size?
nah - just kidding. I do have a real question though - How did you meet [your buddy's girl]? What do you think of them as a couple?"

You can make the questions up yourself - but make sure there's a reason for her to reply and that should hopefully get the train back on the track.
It is probably like your train got derailed because of the situation and once it's back on the track you can again follow the usual route round the track.