Based on what you told me before, I assumed she was interested:
Seducing the Boss
But from what you're saying here, with how long it's dragged out and what's been said, it sounds like she just enjoys flirting with you and is getting a kick out of it. The "If we're going to sleep together, we might as well date; but we can't date, because I'm your boss!" line. If you've tried everything you can think of and it hasn't worked, it's time to write her off as a flirt and not an actual girl who's interested in you and start meeting new women.
She's probably somewhat interested in you, but she's firmly in control. Nothing's going to change until you start dating other women and she realizes she's got some competition and her flirtation no longer has you under its spell.