RL, I'm sorry that you had a major blow up, but it's been bubbling for quite some time. Now, the tart knows what your h hasn't been sharing w/her. Let the chips fall where they may. I strongly advise you not to have any contact w/the tart. She's not nutty, but very sly and cunning. She knows exactly what she's doing and I would venture to say that this isn't the first con she's run on a man.
Do not apologize. She's a third party in your marriage and does not belong there.
Sending positive thoughts your way.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.