First, you did not answer the main point. The main point is that she did not put herself voluntary in a dangerous situation. The fact that some ICE agents were unhinged and dangerous is not something that a normal citizen should expect. And as far as I know, she was just at the wrong place at the wrong time.

But second, your example is moving the goal post. You started by saying "the onus on her". Then you say "when I'm next to my family member that has a gun, I'm almost automatically more careful". But the onus is on your family member. Are you seriously saying that if your family member would shoot you, you will agree that the main responsibility is on you?

And where do you put the bar? Does it mean that if I carry a gun, people should be extra careful next to me and please all of my requests, because it is "on them" if somehow I get angry and shoot them?

This line of reasoning is just so bad. It is "unfalsifiable": you can use this argument anyway you want to blame any people in the situation. Why did you not say "well, the ICE agent should have known that this woman may be dangerous, so he should not have acted in a way that led to increased tension, the onus is on him". And if the ICE agent would have been the victim, would you have said "the onus is on him" for not having been more careful?