Sunny, Do not send the messages to the guy's fiance. If he is doing things behind her back, she will catch on quite quickly. As for your w, she may have been doing all of this flirting to see what your reaction would be or just to get you some gas. They love to jerk our chains and enjoy watching us twist and turn in the wind. Don't give her that pleasure. The less you react to her behavior, the better. They crave attention, whether it is positive or negative...they don't care.
What I would suggest is that if you still have the messages, print them off or store them in a safe place.
I just wanted to let you know that my DB phone coach thinks I should print out copies of the text and give it to his fiance - she really gives much different advice then here a lot.
If someone decides there is no goodness in you they won't be able to see it. I'll take a BLT over a MLC anyday !!!