I'm finally doing a watch-through of Kevin's Choice, and the episode has me 100% convinced of a couple of things:
1) The prohibition against interacting with others and giving up your old life is less of a 'hard and fast' rule and more of a 'guideline', albeit one that Kevin has latched on to as a personal indicator of one's level of dedication to the Samurai lifestyle and the duties of being a Samurai Ranger
2) Dayu's angst and issues have less to do with what actually happened to her and Deker and more to do with the way she's 'internalized' what happened to her and Deker, with her having latched on to the image of a 'perfect wedding' and her physical Harmonium as a way to deal with her angst and issues and cope with what happened to her and Deker. In a way, the symbols of the perfect wedding and her Harmonium have become more important than the actual circumstances surrounding Serrator tricking her and cursing both her and Deker.
Note: I'd actually become convinced of Point #1 earlier on in the season after being able to watch the first 10 episodes of the season in their proper chronological order, but Kevin's Choice just further cemented things for me.
Edit: I'm in the process of watching Runaway Spike now, and the Dayu/Deker scene in the episode only further illustrates my second point.