anyone else simply watching the scene from a distance feeling even slightly any emotion is justified to shoot her to death as a form of self defense

That really depends on your area and what witnesses exist to corroborate your testimony. You can’t just “say” you felt endangered just because a gun was drawn, it needs to pass the “reasonable person” standard (i.e. would a theoretical “reasonable person” feel threatened in this scenario?). I’m guessing an elderly woman pointing a firearm at an individual who is clearly harassing her doesn’t present a danger to a reasonable person who isn’t in the line of fire.

That said, if the elderly woman appears jumpy or something, maybe there’s a case. But it’s not an open-and-shut case like shooting someone who is taking hostages or something.

Source: am American in gun-friendly state who reads news articles about justified and unjustified shooting cases.