For all of the people asking "why does she want to tell the wife now, after the fact?"
Let me say this, I am the OW. My DH left his first wife for me. They had no children but I doubt hewould have left her had I not gotten pregnant as a result of our affair.
So, here we are 5 years in and actually our marriage is pretty good on paper. By all accounts, his ExDW has forgiven him. I would really like the opportunity to apologize to her directly. We've never spoken since she discovered the affair, but I am nervous about how my apology will be received.
So I think it's a pretty natural thing to feel remorseful for sleeping with someone's spouse, no matter the outcome. Even emotional affairs, you're messing with a marriage. It happens, though.