She bears some responsibility, for sure. But Baldwin pointed the weapon at another human being. Baldwin pulled the trigger.
That’s on him and him alone.
Negligent homicide at minimum.
I agree that Baldwin bears some responsibility, because it is standard practice in productions to always 'cheat' the aim when 'shooting' someone on camera, just for this very unlikely possibility.
However, I believe that they were filming a closeup scene of Baldwin shooting someone from the point of view of the victim. This necessitates that Baldwin point the gun at or very close to the camera, and both the Director of Photography and the Director were standing next to the camera, where Baldwin was required to point his gun.
That's how you get scenes like this:
But it is the Armorer's job to keep the prop guns secure, to make sure they are properly loaded with the required dummy or blank cartridges required for the scene being filmed, and to MAKE SURE NO LIVE AMMUNITION IS ON THE SET, EVER.
She is the one who should have triple-checked the firearm before handing it directly to Baldwin.