When you talked to me about you and M in May, I told you all of this. I told you how much it would hurt me, I told you it would damage our friendship, and I told you how I felt about all of it. But you chose to pursue the relationship anyway. You made a fully informed decision knowing what the potential consequences might be and you proceeded anyway. And then you were surprised by my reaction and upset at the natural consequences. I feel like you didn't really think I would get mad, so you went ahead and did what you wanted anyway, then when I did get mad, you tried to place the blame on me.
I was prepared to walk away from you and M and never look back. I thought maybe someday you and I would be able to work things out, after he left and your relationship disintegrated (which I still think will happen), but now that there's a baby involved I can't walk away. Now, you and I will be forever tied and I will have a constant reminder of how hurtful it was to lose my best friend. And, somehow, everyone thinks that because there's a baby involved that all my hurt feelings will just disappear. But it doesn't work that way! You know what would help make the hurt go away? Some kind of acknowledgement of the fact that you hurt me! An acknowledgement of the fact that you betrayed me and threw away 10 years of friendship for a guy, a guy who is most likely cheating on you and will continue to do so as long as you're together.