In the standard relationship when people break up it is because there are problems between them, good reasons not to be together. I think it's hard to wrap your head around the idea that there are no issues directly between yourselves and yet you still must be apart. I frequently find myself saying, "This is just stupid."
In my own situation, I know my friend was pain, but I do feel some underlying anger at her for agreeing to a permanent triad and then changing her mind, with the added bonus that she was shocked that we were hurt when it was she that "had everything to lose." Nope. I feel like I've lost everything. It might have made it easier if she'd tried to understand how much this hurt both her husband and I.
It's been 6 months now since I left.
As for her marriage, it is forever altered. Yes, he is staying with her. I'd been working under the impression that he was motivated by love and honor. He told me yesterday, that his motivation to stay is almost purely driven by the fact that his kids are flourishing, and it physically hurts him to consider ripping that apart. He does well in his role as husband, trying to keep the lines of communication open and endeavoring to support her, but she is no longer his focus in life. Sadly, I believe in the long run she will find that she has lost more than she realizes.
That said, my friend is going through some changes. Whether this will eventually result in her come to some understanding of the situation, and sympathy for our losses, I don't know. Whether this will enable her to repair the relationship between them, I don't know. Time will tell.
In the meantime, I have to move forward.