Karen Margrethe's reproach

When Ulrik walks into the car shop for the last time, just before being fired, Karen Margrethe can be seen talking to Merete. From their gestures and body language, I got the impression that Karen Margrethe was giving the younger woman a dressing down. However, I'm not sure what complaint she could make. Could she say that Ulrik was her tenant, that he watched Polish television with her and had sexual relations when she demanded it, so that Merete was therefore encroaching on her territory? Although these points are true, they make her claim to Ulrik seem very weak. Further, Merete could answer in all honesty that Ulrik had denied sleeping with other women. Nonetheless, Merete looked abashed to me, so I wonder if there was some truth to Karen Margrethe's accusation to Ulrik that M. was a loose woman, even though she really didn't seem easy when U. met her. What do others think was being said?
I also wonder why Ulrik stayed out of this. Since he had already taken the step of telling Karen Margrethe that he had met someone else, I would have thought he was at least committed enough to Marete to stand up to Karen Margrethe.