It was excessive, she had concussion afterwards. He didn't give her opportunity to calm down, there is a longer video, which shows he grabbed her and slamed her, rather than restraining her.
I saw this on FB, there's been a lot of violent incidences against children as young as seven, coincidently, they've all been black.
It's interesting that there was a video showing an Officer kick a man to the ground, who had full motor bike gear on (so he could be seen as threatening), yet all of the comments supported the White adult man who'd been assaulted.
Yet the comments are mostly a lot less positive about the black students that are assaulted and sometimes sexually assaulted by Officers (and ignored by fellow Officers/Staff).
Some of the US Police do seem to think that they are above the law, especially when it comes to female and black/minority 'suspects'.