I don't get the 'crash and burn' part of this, SP. I think you did ok for yourself. You sound like you were the one most in control and reasonable. She is out of balance ("FINE! I'll stay....And you're going to suffer..."). Angry. Grasping. Desparate to get you to give her permission to do what she wants ("Gosh, W...I hadn't thought of that. You'd better go then with my blessing b/c I sure don't want that kind of life.")
You stated a belief you hold. You validated ("I understand why.") You called her out on putting words in your mouth. You were fair.
I think you did fine. Do that a few more times in a row and she'll begin to see that you are a brick wall of integrity.
Cheers ~~~
Me45 H46 T25 M22 S21 & 19 D13 Separated and filed 8/08 Moved home 11/08