Sounds like you let your emotions get the best of you. We all make mistakes in this process, so don't beat yourself up. You do need to take note of how it got you nowhere, though, and learn from that. While you did make some valid points with W (and glad you didn't let her push you around in blaming you for the A!) it just doesn't do any good to argue with someone who is not going to be reasonable or emotionally mature. It just makes you crazy!
Think about how you should have acted - what the better response would've been. That way you'll know better next time what to do with yourself and be prepared for the emotions that sparked it all.
