Life After Betrayal

IMO you should put her aside and no longer communicate with her. She WAS a friend. She violated the friendship. She's history.

Concerning your boyfriend , he learned a lot about you and women and what is acceptable and is not acceptable when involved in a relationship. I think you should move forward with him and put this insident behind you both. HOWEVER, if I were you, I would be VERY AWARE this is 2009 and temptations abound everywhere and there are many girls who may want to entice him away from you. SO I would be watchful and watch him and keep tabs on the relationship while moving it forward. By moving forward I say, what do you want from this relationship?  Life just works out better if it follows a prescribed course of the appropriate things to do in a timeline, like; courtship, engagement, wedding plans, wedding showers, looking for a place to live together, marriage, planning for the future, planning children, shared hopes and dreams.  Once you start messing  with the prescribed pattern all a person has is a failed relationship. How honorable is that? I don't know if that is better or worse than a failed marriage but at least you are on a conventional path if you work on moving the relationship forward. Things can get so messed up if you diviate from the path.    So good luck to you. You nipped it in the bud!  Congratulations!

The BF seems to have screwed up at least one and half times [once with the friend and once with the other woman], and the friend only once.  You don't say how strong your relationship is with the friend, someone you only grew up around, but not really friends? someone who has been with you through thick and thin?  Somewhere in the middle?  My advice is on the assumption that she is a really good friend for a long time. 

Unless you see a strong chance for a lifetime with the BF, I would mend fences with the friend.  You had/have a lifetime with the friend, and I don't know how long with the BF.  I have had to choose between long time friends and GFs and I chose the friends.  My friends are still with me, and I found another GF who is now my wife.