In a way, a way you can't really appreciate, you are lucky. She showed you the type of person she is. Didn't have to take her word for it, she showed you in unmistakeable terms. Its far easier to detach now, without the baggage of marriage, a mortgage and kids. Far easier.
Now, your rule is NO CONTACT. There is no reason to be in touch with her or to respond to her attempts to reach out to you. Its Over with a capital O. No phone, email, text or face to face. No contacts means no new hurts.
The why of it all and more details will not help you. She's the one with her head on crooked. You can't figure them out. They probably can't figure themselves out.
No team goes undefeated. Good teams pick themselves up after a loss and prepare to win the next game. Take that sports analogy and run with it.
And your bf? Well, ever hear the saying "he is dead to me" ? Used by Michael Corleone in Godfather II when describing his future relations with someone who betrayed him. It may be his exW, and he didn't literally have her killed. He just refused to have anything to do with her and slammed the door in her face. Take a lesson from that. Pretend he is in fact already dead. Don't go kick his ass, trash his truck, etc. It isn't worth it. You'll have a few minutes of satisfaction but it won't last.
If you never see or hear from either of them again, you are better off.