if henry was super awesome sugoi and had as much aura as josh, he would've moved faster than time and manually maneuvered her so that the gun was pointing away from chase and then started moving normally so that by the time he shoved her arm away, the gun would've been pointing at the floor and he would've tackled her and looked super cool in front of chase, josh, and probably isaac (idk what he sees in that guy tbh), but alas
(LOL but i was thinking about that after i left this comment lol i think if she felt any pressure from henry pushing her, her finger would've pulled the trigger, but i also think henry's abrupt movement probably startled her which is why she shot the gun)

why didn't henry just neutralize her he was standing right there