StanT: thanks, I wanted to say something similar, but couldn't really fit it into words.
the sentence: there's so many little things we do, just doesn't work. If we don't notice them, it's that we really didn't even think about it, or would have done it ourself if we thought it necessary.
On the other hand, if she says no, and you take the effort to read the yes through the body-language, the way Tecoyah says, why not use it yourself?
She goes no, no, but shows all the little signs, then rightaway, treat it as a real no all the way, and see if she doesn't wise up
I've done that a few times and they do catch up to the fact that you apparently can't read their mind afterall (or maybe I was just lucky
)
edit: d'oh, axiom_e beat me to it with a similar post