If you will go back and read about having a great day with her, and even were playful, look at the conversation topic. You were not fighting her about the D, so she thought, "Hey, he's going to give me what I want and he'll still be my best friend".......and you were not seeing that at all. You saw your W acting happy and like so many men do, you weren't LISTENING!!! You thought things were in an upward swing.
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!