FOR ALL YOU KNOW, if the officer had not STOPPED the girl (who was ranting and challenging the cop, and advancing on him), she might have convinced the group of 'yutes' to gang up on the cop, who might have then HAD to use his weapons to defend himself, resulting in some deaths.
BE CAREFUL what you 'wish' for.
OK maybe you are not understanding the concept of riot control and techniques to de-escalate a situation.
She might have done that- there are techniques to stop ringleaders in a riot situation.
That is one of the steps- AFTER to make sure you do not escalate the situation yourself, you try to identify the ringleaders who ARE escalating things, and you remove them
Crowd mentality is a very complex thing. If you remove the ringleaders, the riot usually dies.