I wasn't there, and I'm not her, so I cannot say what she was feeling. I do think that she did what she felt was the best option. Personally, I would not get out of my vehicle to confront an aggressor. If they need to be shot, I can replace my windows. I'm not putting myself at greater risk by exposing myself to an aggressor. I'll wait for an on duty officer to show up and arrest the aggressors.
Sometimes, while not lawful, a gun needs presented to calm down the situation.
It's not always necessary to take a life. Just because the law is very dumb about it doesn't mean it isn't valid.