Ah, the head shake. She typically does it when she isn't following someone arguement or logic, and it usually is accompanied with a WHAT! I have seen her do it often, she likes to debate politics, religion and the like with a lot of friends.
When she accepte the invite for a bagel and coffee it was a no brainer, and then it was all the sudden stop walking, wait WHAT? I'm sure there was some little internal debate about why is he doing this or that?
