At the 2-second mark, you can see a man in shorts enter from the left while his arm comes forward underhanded as he tosses a handful of something into the crowd of officers. The woman was hit by this same volley. Not once did she ever raise a hand to spray anything.
I don’t think the guy on the left throwing anything had anything to do with the officer’s action. Watch her actions from the start. She was taunting the cops or saying something to them that they didn’t like. That is why when the sergeant turned around she retreated. She knew immediately that he was coming after her.