Looks like she was climbing through the broken window holding an american flag, and was shot for it... now that I look at this again.
There are COPS literally all around this woman. Not really sure why THAT door was where they decided the boundary was for lethal force.
Some of the videos show at least 5 armed Capitol Police herding her with other people up the stairs and into the corner where she was shot.
The police on the outside didn't seem concerned at their proximity to the crowd, though one reflexively raised his rifle at the shot, but lowered it right away.