This round all started when I lost my temper at a party where she disappeared with a "friend" of mine (male, who had betrayed me before) for 30 minutes or so, and I completely lost my cool with both of them, very wrong, but, nonetheless it happened. 15 minutes of my "outburst" over something that I perceived to be very real (she had an A in March 2009), should unravel everything we pieced back together for the better part of a year.. Am I being unrealistic ?
FWIW, I don't believe that is what did the damage and pushed her toward wanting a D. She may want you to believe that was it (and you gave her an excuse) but that is NOT the reason she's asking for a D.
You need to get off the roller coaster and have your own life. Stop looking at her to gauge what kind of day or night you have.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!