I think that is her with her back turned and hands on her hips. In another part of the video, you can see she has stripes on her sleeves. This makes her the ranking officer on the scene and responsible for the actions of the other officers.
As a former Army officer (active duty 1968-1969) I still remember having it drilled into me that, "An officer is responsible for everything his men do or do not do." If one is looking at a group maneuver, like the Garner takedown, the ranking officer on the scene is definitely the one responsible for all that happened, just as a platoon leader would be in the military. Indeed, with a borderline hold, like the one used on Garner, the propriety of the hold was the sergeant's call; hence, she should be as accountable as, or more accountable than, the officer who applied it. In turn, it's the city administration and its police chain of command that deemed using such an excessive level of force and huge police presence appropriate to deal with one genuinely non-violent low grade petty criminal, and did so because of its fanatical desire to enforce a draconian revenue law that deliberately exploits the addicted poor. When Comrade Bill and El Presidente Obola say this was caused by racism, they're just trying to deflect accountability from their own fanatical socialism that actually killed Garner. After all, only one or two cops are all who are usually necessary to stop a drunk driver who is a real, immediate menace to public safety.