Daphne’s point was made when everyone was quiet. Mum was the only non magical person in the castle. She was also in a position of power and it caused a slight tiff with certain people. There have been a few times when someone had to interfere before Mum decided to get.. confrontational. Honestly, I wouldn't have cared if she did, but appearances and all are important. Mum was sort of the figurehead to the mages as the only non magical that most of them have ever seen. 