Hmm, I like that interpretation too, because again, it is literally true, it IS the first time the Halo does something for someone else. And only time? Hm.
Well, both those theories work together, either way, it was reacting to Ava’s extreme feelings of fear for and protectiveness toward Beatrice, which, of course, you see a friend about to get shot, you react, it could have been anyone, but that’s the thing, it could have been anyone. Instead, they wrote it as specifically Bea. It’d have made the most sense if it was Mary, Crimson taking her own gun and turning it on her, and they’d just finished bonding in ep 6 and then reuniting in ep 7, but instead it was Bea. Well, intentional or not, for whatever reason the writers felt how well it’d work with Bea and they were right!