Mate, you better ask yourself this question and answer yourself true:
Am I still 'IN LOVE' with my wife, or do I just love her for all we have been through?
If you are still 'IN LOVE' with her, make a point of telling this other woman that flirting is not OK, and make it clear you don't want anything more than a work relation with her. YES even if it makes you look like a dickhead, and she says she wasn't interested etc. JUST DO IT!
On the other hand, maybe shes the one, maybe this other woman is the real love of your life. I have no place to tell you otherwise, my friend was married for 2yrs and fell in love with his wife's best friend, they have now been together for 8yrs happily married with 2 kids, so who knows these things.
The only advice I would give is this: If you want this other woman, be decent enough to leave your wife first, don't have an affair, you owe her that much at least mate, be a man.