All you can do is let her know that if she ends her affair and comes back to your marriage, you will be the best best friend and listener she's ever had. But you can't fill that need of hers as long as there's a third person in the marriage.
I will tell you this: it was the missing of my FRIENDSHIP more than anything else that caused my wife to break. Wish I could say it was my studly bod or my incisive wit, but nah -- it was the sharing of her day, good and bad, that she told me she missed the most.
