After her first one the threat, if any, was neutralized.
So then why the second one???
The first one may have been SYG --- but the second one is murder.
Any firearm instructor will tell you that a double tap is a time honored method that develops accuracy and ensures your target is down. All that indicates is that she was a trained concealed carry permit holder.
Maybe he didn't drop right away.
If self-defense was justified for the first shot, then it's almost certainly justified for the second. Unless she got out of the car and then finished him off as he lay on the pavement.