You know, if my best friend slept with my BF in order to “piss off” my BF’s best friend, I would have to take a second look at our friendship.
Obviously, it is not reasonable to sleep with ANYONE in order to punish someone else. Your friend needs counseling, and you realize that. In fact, you seem to feel forgiving toward her because she is not emotionally or mentally well. (Not making a judgement, I just couldn’t really tell what her exact problem is.)
Having said that, what kind of “friend” chooses to punish a third person by totally disregarding the feelings and situation of her “best friend?” If she felt the need to punish her BF by sleeping with one of her BF’s best friends, why didn’t she choose to sleep with one of his best friends who was not involved with HER best friend?
(That last paragraph has confused me to the point that I am not sure even I know what I mean. However, I will press on, and hope you understand what I am saying.)
The fact that you forgave her, and she apparently promised not to do it again, and then did do it again indicates to me that she is acting out some resentment or anger toward YOU.
Perhaps she is jealous of you, or of your friendship with her sister, maybe she is resentful of you for other reasons.
I believe that forgiveness is always the way to go. Not for the person you are forgiving, but for YOU. Hanging onto anger hurts the person who holds it more than the person it is held against. IMHO.
I would say, forgive her, tell her so, and tell her that since she has shattered the trust in your relationship, she will have to build trust again. It is one thing to forgive and another to forget. Forgiveness cleanses, but it doesn’t mean that you should forget and leave yourself open to being stabbed in the back again. It is healthy to fail to trust a person who has demonstrated that they cannot BE trusted, time and time again.
I would also NOT introduce your current BF to her without explaining to him what happened in the past. If you tell him what happened, and explain that you suspect that this may be a pattern of retaliation for resentments toward you that SHE has that you have not been able to understand, or deal with since you are not sure what they ARE, your new BF will be able to factor this into any passes she makes.
If this should happen, and he should respond to her as your former BF did, then you will know what you need to know about him as well as her. If you don’t warn him ahead of time, and he views her as your friend, he may well be unable to know how to deal with a situation where one of your best friends makes a pass at him and he doesn’t want to offend her because of her “friendship” with you. You may lose him in whatever capacity you want him in your life because he won’t want to tell her to buzz off for fear of offending YOU. Lots of men would just bail from a sticky situation like that. Can’t really blame them, IMHO.
I know that I am going on and on about this, and I apologize. This strikes a nerve with me, because one time my best friend’s husband made a pass at me. I was horrified, and crushed. My initial reaction was “What did I EVER do to make you think I would be receptive to this?” He said that, no, I had not given him any indication that I was interested in having a relationship with him. He said he was really attracted to me, and thought he would “give it a shot.” It made me sick at heart, and I didn’t know what to do-should I tell my friend, or not? I did not tell my friend, instead I distanced myself from spending time with them as a couple. My friend felt hurt, I was a basket case and it was a total horrible experience.
Of course, eventually the husband found a less ethical person to have an affair with, and the marriage ended. What a slimeball.
So, to get back to the OP.
Forgive her, but don’t trust her as far as you can throw her, (as the previous poster said) if she was tied to a bulldozer. (Don’t remember who you were, but good statement!) Good people are good people, screwed up or not. Bad people are bad people, screwed up or not.
Move toward the light by forgiving, but retain your feet on the ground by accepting that not everyone is seeking the light.
Scotti