Reasonable. And it makes more sense, too. Being a Vulcan, she'd shy away from being sadistic.
While I'd like to think she would --- a Kantian could argue that the evidence of Mirror Spock's openness to decency indicates that she would --- I'm not sure it follows. After all, a person who's committed to murder has accepted at least some sadism. And if the point is to kill a person without being traceable, whether the person suffers along the way is irrelevant.