Three SWAT guys right behind her did not see her as a threat.
Second guessing the actions of others in highly charged situations like that is a very difficult art.
There is a long version of the video that shows the uniformed Capitol police who were in front of the door leave just before the window is broken.
My question is why and who told them to leave?
The whole thing looks like a planned hit to me and that Ashli was set up to be killed.