It sounds to me like DM's old lady made it quite clear she would not be a cooperative witness. If today wasn't a court date, I'd imagine this means she laywered up, too. That's usually what makes these cases go away. Prosecutors tend not to drop them unless it is clear they have no other option because they know how problematic domestic violence is and how bad it would be if the next incident results in the death of one of the parties.
Under the supervision of a local prosecutor, I have actually handled a couple of domestic violence cases. I've seen more than that. There is always the chance that they go sideways on you and you lose them. It didn't happen to me because I was lucky enough to get witnesses who were cooperative. If you get into the case and the witness won't answer your direct questions about what happens, there just isn't much you can do. It's one of the more frustrating things about being a prosecutor from what I saw.
ETA: I'll add that there could be very good reason why she would not be cooperative. DM is to be presumed innocent by our justice system until proven guilty. It could be that there is a perfectly rational explanation for all of this and that DM and his woman will live out a life of peace and tranquility. I wish that on them.
