Stop engaging her. She was upset at the message. You didn't need to add to it. You should have said something like, "I understand why you would be upset at the message". Then let her rant.
By talking to her, and actually apologizing that just added more fuel to the fire. She wants to play the blameless victim and needed someone to blame it on. You were the easy target and actually made the target bigger by taking blame.
You need to understand that what you did in the past was the past. Stop beating yourself over it. Now is the time to move on. She is latching onto that "hurt" because she was embarrassed and hurt but can't bring herself to accept at least part of the responsibility for your sitch.
When she rages against you, move to the other room. When she accuses you of taking sides or demands that you take the blame, calmly tell her that she is entitled to feel how she does, but you are not required to sit there and listen to her.
This is where you need to start taking some kind of stand for yourself. Believe me. My W did the same thing. She accused me of so many things, I started believing them. There came a point where I sat back and said "WTF? That's not true" and I started to stand up for myself. Not in a mean way, but started stop being afraid.
Women don't want a man they can control.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.