Wait, let us find out more about this chick, if her T is relatively low, then perhaps she does know, but if it is relatively high, she probably doesn't.
Also, in what ways was she flirting?
My sister is very much so a one-of-the-guys type of gals, and she has a bazillion more male friends than she does female ones.
I think this woman is being methodical in the ways she is acting towards your fiance, unless of course, she *genuinely* likes him, which might be a possibility.
However, I think the fact that she has no idea that you dislike her acts as evidence towards the fact that she does not actually fancy your fiance, but rather views him as a person who can get her a promotion she so desperately wants.