Don't blame you for feeling angry. You seem to have been blindsided by this.
Were there any tell-tale clues that she was this unhappy? Sometimes with space, you can look back and start to put the pieces of the puzzle together.
You did a good job of controlling yourself and staying calm during your talk with her. Keep reading over Sandi's 37 rules and memorize them, they will definately help.
Lastly, hang in there. This is going to be a tough road but you can do it. We all remember the feeling of the bomb and the first few weeks afterwards. Gut-wrenching is the only way to describe it. Chin up.