Hey. Met made contact with this HB9 not that long ago. We were like 3mins into our convo, things were going quite well, she was isolated and somewhere along the line i thought it was appropriate to start qualifying her.
I said, "your pretty hot, but beauty is common, what makes you special?" I meant it in the kind of get-to-know-you way. My body language and such was congruent with what i wanted but I noticed her facial expression suddenly changed from warm and open to closed and defensive. When I saw this my blood froze and i knew that was the end. I rolled off as soon as i could and came here. comments greatly appreicated.

If she's attracted to you already (which she is if she will let you isolate her) and she's a little insecure, she's bound to get pissed off at that. She was probably expecting to get to know you or for you to make out with her or something, but when you just come out with a line like that makes you sound like an arrogant dick, and she feels like she can't win you over, so she gets defensive on you. If you're gonna qualify her, use something more positive sounding/complimentary rather than being too challenging, or use cold reading to encourage her to get talking, e.g.

"ok... you weren't always this pretty were you?"
"ummm, why?"
"well it's just that you have a great personality and you're very friendly, it's rare for such a beautiful girl"

Then you can move on to that question because she knows why you're asking.