(the following is a meta-analysis of events in vampires smp that looks at the real people's motivations behind their character choices, and switches between discussion of character and creator.)
when scott is manipulating apo into becoming a vampire in ep3, he presents her with a false choice. apo shows up to the meeting alone, refusing to victimize another human to save herself, and so the stakes are understood by both of them as follows: either scott turns apo, or he kills them without turning them. this is the crux of the dilemma he uses to manipulate her into "choosing" vampirism.
in terms of the actual game mechanics, however, a vampire killing a human without turning them would be very difficult, and may even be canonically impossible to do. in this mod, killing has been replaced by the turning mechanic: if a vampire delivers the killing blow to a human, this automatically turns them into a vampire. the only exception to this rule is a mistake—it's when martyn falls off the bridge while running from scott, and dies to fall damage rather than to scott directly. on a meta level, this death clearly isn't an intended outcome, so it doesn't count. in-universe, it's played off as martyn being seriously injured, falling unconscious, and apo "carrying" him back home off-screen.
scott, who insists on metagaming multiple times in the same episode, is well aware of this. in fact, by presenting this threat to apo, this is yet another act of metagaming! it's a subtle one, but knowing scott, it's hard to believe this wasn't on his mind.
apokuna, being one half of pow creations themself, is almost certainly also aware of this on a meta level, but she's serious about this rp shit. so apo the character has to take this at face value. she can't call scott's bluff; they have no reason to believe he's bluffing. on top of that, it would make for a really lame conclusion to the scene if she just ran away and didn't let scott kill her. (if the roles were reversed, i'm almost certain scott would choose to run away, but that's neither here nor there.)
essentially, apo's fate is sealed the second she shows up to that meeting. but scott could have accomplished this anyway without the empty threat. so why did he bother? well, scott recognizes in apo a legitimate threat to his current position of power. the second apo said they know scott likes to play games, he knew he had to pull out all the stops to not just turn her, but to make sure she walks away defeated and discouraged from making another power play. apo got him dead to rights, and he even admitted the truth in front of her, that he only likes playing games he can win.
so, to add insult to injury, he presented her a choice with only one viable option. he got her to verbally agree to being turned. not because he respected her autonomy, not because he valued her permission, but because when it comes down to it, scott will stop at nothing to win.