No it would make sense to subdue her. Subduing the first through the window would perhaps dissuade the rest from going through the window.
Regardless of anyone else assaulting that window/door she was unarmed and did not constitute a threat to his or anyone else’s life.
And by your reasoning it only made sense to shoot her if he was there after going to stand quads over that dood/window to preclude others from climbing through that window.
Byrd gave no warning, Byrd stepped forward, shot Babbit and retreated and was not seen again.
If Byrd was defending that hall way his actions only make sense if he continued to defend the hallway after shooting Babbit.