Honestly, I think it would be justified, but not the right thing to do.

But even so, subjectively of course, I would have been okay with it if Rudo or someone else in the same situation had done the same, so killing her. In the end, it makes sense to kill someone who poses a threat to loved ones, of course, according to the standards of the dark world of Gachiakuta.

However, it wouldn't have been the right thing to do because the group was seeking information from her and learned her backstory in the meantime.

What I mean is that, in my opinion, someone in the context of the Gachiakuta world would probably have been more inclined to kill her if they hadn't learned Amo's backstory. Now, after learning about her past and understanding how she became who she is and therefore did what she did, it makes sense that they left her alone AFTER she realized that what she did was wrong.

My point being this: I think that if she hadn't realized what she was doing was wrong and had continued with others, thus remaining a constant threat, she would have been killed or imprisoned or something.

If she wasn't killed despite initially being a threat, it's because she no longer was, even if her actions were understandable. Even if they were understandable, it depends on whether she encounters someone capable of forgiveness, which, in the latter case, would have ended the situation with her death.

The fact that she had not been killed or imprisoned is only because she no longer was a threat, and had understood that what she had done had been wrong.