Detective, I agree with what you said in your post, those things struck me as well.
Bultabee, be careful of black and white thinking. When one person in a relationship is unfaithful, it's easy to blame them and heap support on the other person. However, in a marriage, and especially one that is not new, there are ALWAYS other things going on. It's easy to point the finger and try to make one person innocent and the other guilty, but that just isn't the way the world, and relationships, work. I'm not excusing her behavior. What I am saying is that obviously she had needs that weren't being met in the marriage. Human nature being what it is, eventually a person will go looking to have those needs met. A good marriage counselor could help them uncover what other problems exist, the ones that led up to her affair, and if they are willing, there's a good possibility that they can work things out.
I have to agree tho with the other posters who have cautioned you against too much involvement; you could end up losing a good friend, who might really need your support right now, or even getting badly hurt. Be careful.
Dana