I confronted K last night. I told her that what they had done behind my back was not just a betrayal to me, that it was a betrayal of our friendship. I told her that I still love her as my friend but I don't trust her as far as I can throw her right now. I told her that I am willing to forgive but she has to work on getting my trust back, and that there isn't any specific thing she can do to fix it. I told her that if she truly wants a to be in a poly relationship with Abe and I that she has to talk to me as much as she talks to Abe about how she feels. That if it is a relationship with both of us she wants then it has to be both of us, not just one, that she communicates to. I told her there are no 3rd chances, this is her second and last chance. I told her that if she truly wants a poly relationship with us, that she is also going to have to tell the other two men she's dating that she is dating us. Told her that once that once that bridge is crossed that her lying to them does affect us, and that if she continued to lie to them, that I could never trust her to not lie to us. I told her that Abe had asked that I not bring any of this up and not confront her for her role in this because he didn't want her feelings hurt, and said that that was unacceptable. That I refused to be the only one who's feelings were allowed to get hurt, and that I didn't do anything wrong in this, so I refuse to feel bad about hurting her feelings. I told her that I expected more out of her than I honestly did Abe. Abe has always been clear that he's not mono and that he never could be, and while yes he broke our rules in not talking to me about it first, I knew it would happen someday. But that I expected her to have the control to say "No, we have to talk to Thunderzag about this first" and she didn't. I told her that right now, no, I really don't trust them alone together. I told her I am a forgiving person and that I suspect it won't take long before I start trusting her again but that I really can't give her an exact timeline. I told her that condom rule we have will remain in place until she has stopping seeing one of the guys she's dating and has been tested and that other forms of birth control have been put into place. Abe and I have been trying for a baby for 4 years now, and have had one miscarriage 3 years ago, so no I'm not ready for her to get pregnant by him, especially while I'm still hurt and angry.
She told me she completely understood. She apologized for betraying me, admitted that she has gone most of her life just doing and not thinking and that she had been lucky that it had never had adverse consequences. She said that she does truly value our friendship and that would rather us all just stay friends and cut any sexual or committed relationship ties with Abe than risk her friendship with me.
I still don't trust her, so I'll see how it goes. At least she did admit and apologize. Finally.