I'd like to add....

It seems like you value this female friend more than she values you. You're stressing out about losing her, but at the same time, she pretty much drops you when she's with someone else. That's not a mutual sort of friendship.

I never said relationships were easy, but I do believe that you're inviting drama into your life and making excuses for doing so. Why are you being so disrespectful to your wife? (Yes, you are being disrespectful to her. If my partner cheated on me and then insisted on being friends with the woman he cheated on me with, then the relationship would be over....I don't care if it was with his childhood best friend of 30 years. I don't think you can comprehend how big this issue is because you can only see what you personally want, not what is best for your marriage or your wife. Good luck with your selfish attitude in the future.