You have to make up your mind before she opens up. Either you forgive or you don't. Go ahead and imagine the worst. Just for argument's sake. With your two best friends. Multiple times. I hate to say that, but truly make it the worst case scenario. And then TRULY think about whether you are willing to forgive.
Another thought is this. I don't know how this would work, so I am mainly just talking about my a$$, winging this, but follow me for a minute. What if you just told her that you forgive her, but that you don't want to know? I mean really, if you want to forgive and move on with her...and she wants to make it right...does it really matter? Does it just make it worse to know? As long as you have her back, do you care what she did as long as she is willing to go to counseling and do something better and different for the marriage. I hate to not know, much like I imagine you hate to not know, but really...could you forgive without knowing? Maybe I am crazy, but it's something to think about. Not sure. Maybe someone else will have ideas about how to cover that.
Have a good night.
Melissa
"Standing knee deep in a river and dying of thirst."