I feel like I want to sit her down and say I know how long your EA was going on for, I know I was duped on BD, I know the commitment you made for the future with him and I know you recently broke your self-imposed N/C. For those reasons I want a D.
I think the LBH has a strong desire to let his WW know he has not been totally duped. Being duped is rough for anyone, but I think it's especially tough for men. When you look at the heart of why you want this conversation, it is about revealing what you know to her. If that's what you are going to do, then you need to have some type of plan before you address it. Know what you want, and know what you require from her in order to proceed with a MR. Don't go into it to just see what she says or how she feels. Don't even say what you require, unless you hear her ask what has to do. It's about what she is willing to do in order to save the M. Btw, she doesn't have to like it or feel a certain way, in order to conduct herself respectfully, and honor her marriage.
FWIW, the first thing she'll want to find out is how much you know, and how you found out. Then, she'll probably try to turn the tables and make you feel terrible for invading her privacy. Don't let her get the focus on her not being able to trust "you". She is the one who has had the secret EA. She is the one who violated trust in the MR. WW's are sly, so stay on your toes.
I have often said if my H had told me he wanted out of our M, it would have yanked me back so fast my head would have spinned. You see, the wayward W is arrogant, and sees herself as the one choosing a better life.....a better man.....etc. It's like a game (if you'll excuse the term). As long as she has the ball, she's going to play the offense, but as soon as he gets the ball, what happens? She immediately goes into defense. She wants to secure the ball. That's why the H will start seeing temp checks from her.
I'll add this side note. When I read Neffer's post about his struggles with the fantasy, it brought back memories of how long I clung to the thoughts of "what if", "what could have been" with OM. This was after I decided to end my A and stay in the M. A fantasy can be very strong. Just b/c a wayward spouse decides to end the A doesn't mean the fantasy ends. The WS has to murder it! It's not going to quietly slip away. It's not going to die a natural death. You have to kill it. This type of fantasy is unhealthy for the individual and for the MR. Once the fantasy is gone, then the love in the MR has a chance to heal and grow.
So anyway, when you decide to confront her, don't go in playing defense. You have the ball.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!