I know nothing of the mother's character, but neither does anyone else in this forum.
I believe that police involvement was appropriate, so did the responding officers, so did the magistrate. And according to records of the video of conversation between the mother and van der Poel, van der Poel himself suggested that they should be called.
I'm not sure what you are saying here: no-one did call the police over kids doing a prank, so who are you describing as full of themselves?
I do not think it at all unthinkable that a woman in confrontation with an athletic and angry man wants to show what evidence she has to the police rather than to him. Nor do I think it surprising that after he has physically intervened, and entered the hotel room of young girls, her priority is challenging him on his response rather than apologising for what the girls had done.