I have been married 28 years and I have seen a lot of affairs and problems come and go with marriages. If you TRULY love your wife, you will tell this friend it is over as you are focusing on your marriage. You will absolutely not contact her again. You will also thank god (or whoever) that your wife has taken you back and forgiven you. You must realize that your wife will never forget this.
i don't care that you slept with this woman, but when you did, you lost the innocence of your friendship with her and your wife's trust.
You need other male friends. Forget the female friends.