The Police woman was just spoiling for a fight, clenching her fists. She had a gleeful expression on her face.
I'm just repeating what everyone else has said here, but she's completely unfit to be a copper. She's nasty, power crazed and vindictive, everything she said and did was entirely unnecessary, not to mention her total disregard for the young girl's disabilities.
That poor girl just needed to be left alone. What's going to happen in future, if she really needs the Police?
De-escalate? She deliberately escalated the situation. One of her colleagues should have called a halt to things.
If, as has been mooted here, there was no viable public order offence and she actually assaulted the mother, there should definitely be a misconduct hearing. I suppose it all depends on how good the witnesses are.