Looking at some video of the protest I suspect it was this guy in the hat and sunglasses that did it:
https://youtu.be/TcmE-9hqxCc?t=93You can see him in his leather jacket, black gloves watching her and her group of friends earlier in the day.
Edit: Actually it's not him. You see the dude in the hat behind her when she gets pepper sprayed.
https://mobile.twitter.com/kiarafrobles