I know, but she shouldn't have allowed him to upset her...
I agree that what you say is a good general rule (imho).
But it could be said that she knows she has very serious obligations, there, in her job, and being arrested would prevent her from carrying them out. So it can be seen as a reflection of conscientiousness, in this situation especially.
It can also be said (and is known to be true) that a highly negative reaction can occur when someone has reason to believe s/he is being placed under arrest, and especially when it should be known by everyone that the person is in the right... and anyone can see she was standing on rock-solid ground and in the right.
In a way, her response to it will probably help reduce these things in the future imo. Maybe just a little bit anyway.