This brings back memories. I personally never found an OM but I suspected an EA for this same reason. Your thread brought back some painfull memories.
Sadly I did all the wrong things and did not db until it was too late. But I honestly believe she had her mind made up years ago. The whole facebook / classmates / secret marathon cellphone calls were simply her way of finalizing her escape IMO.
I am divorced now and in the process of detaching and getting a life myself. I feel your pain as I have been there.
But remember this, things WILL get better whether your marriage surives or not.
Me:48 W:55 M:22 T:23 Bomb:19Nov09 S:15Jan10 D:11Feb10 EA:Confirmed on 20Apr10 Fast track to her divorcing me