There's plenty of retarded to go around in this situation. She was clearly looking for an opportunity to brandish and use her weapon. Like others have said, this guy's retardism and ego wouldn't let him walk off. Since there's not clear audio at least from this video, she may very well say he was verbalizing actionable threats and she was in fear due to him (repeatedly) circling back to her and threatening her.

JLoco summed it up best.