The point I was making is that, at that age and lacking experience, she was in no position to judge the situation. She was reliant on the judgement of the adults around her - which was demonstrably flawed. By 15-20, a person is old enough and (usually) mature enough to make their own decisions. Of course anyone, at any age, will be messed up after killing someone by mistake - but in this instance, she was put in this position by people who she should have been able to trust to make the best decisions on her behalf. They manifestly failed to adequately assess her ability to handle the weapon.
Based on the clip, and the way she was standing and handling the gun, this was her first session with a handgun. Did you just hand your kids an fully auto machine pistol first time out? Almost certainly not - I imagine you trained them on safe handling and accurate shooting with something like an air rifle/pistol first, then worked them up through the levels, making sure they were safe and confident at each stage before progressing to the next.