I'm assuming that there was a "response team" already designated to take someone down if necessary. Police and security teams try to refrain from everyone piling in on a disruptor. It's easier to designate who responds so there isn't a gap in security around the room. You never know if the disruptor isn't staging a diversionary tactic. Not having everyone respond at the same time is standard practice.
I saw the video of the thing a little while ago, and that female guard did move forward to help escort the moonbat out. The still pix don’t show it.
Makes sense...even though it appears that the lady officer in the picture looks disinterested, rather than alert.