She said that about 4 years ago she had a fling with him and that it didn't mean anything but she was aware that by nature I'm somewhat jealous and she wanted me to know in advance so that if I heard something that I wouldn't be surprised.

What the hell man. She cheated on you and just wanted to let you know in case someone else beat her to the punch.

Then she danced with him. That made my stomach turn for you.

I don't know what it's like to be married. That's a huge commitment and very tough to do, and you make promises to each other to make it work.

Honestly, it's probably going to be the foundation of many future arguments, it will always be in the back of your head, and man... she cheated on you. What you felt was special with her, she did not truly feel. Think about that. To me, her love for you is discredited in that when she was building what you two have together, which to me is the most important underlying reason for any relationship, she disregarded it for someone else.

Then she hid it from you, but only told you for reasons that benefit only herself.

She's selfish and a liar. Those things usually do not change.

Even if they do, you now have to live with the fact that she does not feel the same way toward you that you do for her.. and you never even knew it.

Fuck that. I'd be outta there.

Here's some perspective. I was with a girl for 4 years or so. Half way through that we had issues that tainted the relationship. We finally split up because it was just always there, bringing whatever joy we had down that many notches.

I met a girl now with whom these things would never ever happen. It's pure unadulterated love. You deserve that, man (under the assumption you never betrayed her either).

Good luck.