I am so sorry...
But you have the truth you needed,.
I am sorry she didn't see fit to protect your children. I hate it when people are so wrapped up in their own wants they trample all over the needs of their own children.
I wish I was surprised...your kids did not need to be put in the middle of this. I think you wrote she said she was putting herself first...well she has definitely done that.

At least you don't have to wonder anymore. All those outbursts telling you all the things you had done wrong, was just her trying to justify the wrong she knew she had done to you.
Allow your self time to grieve. I understand anger is the first and most overriding emotion. Don't let it drive you to do something stupid.
Remember your kids really need you to make sense of this too. If you think her personality switch has been hard on you, imagine how it's been for them living with her and all these strangers she has brought into their lives.
Don't get me wrong kids are very adaptable, they will be okay.
Just remember them everytime you feel like doing something in a moment of anger.

Your right you didn't deserve this...remember that and hold onto it when the mud slinging starts.

If she had an iota of maturity about her, she would hold her hands up and just quietly do what needs to be done.
But her past behaviour suggests she probably won't.

Steel yourself, and lean on those you can. It won't be easy but there is hope and light in the future.