If this was solely for self defense i would agree with the gun owner who had a right to carry and had the license, however, the article also says she told her son to follow the person even when he was fleeing and pose no threat after he was short, to the parking lot where her son fired additional bullets at her request killing the individual and she also tried to get her son to kill the individual girlfriend as well.
This woman is a pure and violent criminal, she should be locked behind bars away from civil society, you don't use your minor son to carry out a cold blooded execution when you where not at risk and then instruct him to further finish off the individual girlfriends. Its pure evil , lets not sugarcoat it.