Just My Thoughts

I have something on my mind and really I'm not sure whether to discuss this with my friend or just write about it and be done with it. Am I taking something that has nothing to do with me too personally?
As some may know, I was divorced in September 07. Several months prior to that I found out my then husband of 20 years was cheating on me. Our marriage was never perfect. WE married young, had financial woes for the first few years but worked hard and dug our way out of the hole. We were always very different people with very different needs. But we were in love, at least for part of our marriage. After our first daughter was born, my priorities and focus changed. His did not. And then along came our second daughter. Life was busy and ever changing. We really grew apart and grew out of love somehow. I knew things weren't going great but we didn't argue or fuss, we simply lived separate lives. Anyway, in my opinion, he should have left before he cheated. I guess that's the fantasy thinker in me. Regardless of the fact that we weren't in love and lived separate lives, finding your spouse cheating is difficult. Divorce is difficult. It's hard on everyone, especially the children. My best friend was with me the night I found my then husband cheating. She knows what kind of pain I went through. She knows the betrayal I felt. And yet now, a year and a half later, she's involving herself with a married man. I just don't get it. She claims not to like him but she also drops hints about meeting him for lunch. My friend is married also but living in a loveless, disrespectful relationship. She claims to be doing this to get back at her husband. I love this girl too death. But her actions could lead to serious problems for herself, her children, his children and both of their families. You see, cheating, taking something(someone)that doesn't belong to you, hurts more than just the cheaters and those being cheated on. It hurts parents, kids, friends, everyone. She knows that. And in some strange way, I feel betrayed by her. I really have mixed emotions on all of this. It's none of my business.....it's not directly affecting my life.....she's been there for me through everything.....I want to be there for her but can't support this decision. I feel like a bad friend and yet I simply can't agree that this ok in any way. She says the man doesn't love his wife, he stays with her because she's the money maker in the family. To me, it doesn't matter....it's wrong....it's hurtful, it's deceptive, it will ruin someone's life. It may ruin many lives. If it doesn't ruin at least one life, it will hurt many. It's not ok to hurt anyone, whether you like them or not. Yes, she knows his wife. They went to church together for a while. She says she doesn't like her either because she controls him and is degrading to him. And she's bitchy to others. It's still not ok.
So am I taking this too personally? Should I forget about it, let her do what she wants and support her regardless of how it all turns out? Do I tell her how I feel and chance losing a friend? I hope time will lead me to the right decision. I hope that whatever happens, no one gets hurt. I can hang on to hope, right? I'm sure she'd say her personal decision with this man is not related to our friendship. And in one way she's right. But when you're as close as we are and share details like we do, I can't help but feel affected by it. Life.....so difficult sometimes.