^Not near a superfan myself but elements to the referenced situation do matter.
1. It wasn't into a crowd at bystanders, she within said crowd capping the two O'Driscolls she and Dutch had grabbed. However, that second shot easily could've taken Dutch's hand. As such, it also did in fact exacerbate the situation, which yes, could've been avoided.
2. It doesn't take too much thought to realize she had done so in what some refer to as a "moment of insanity". Sure doesn't justify the previous points but the trauma from what the O'Driscolls had done to her would definitely trigger that sort of reaction, especially when it's the only way within her capacity to seek some kind of closure.