That is a very good point, something that stuck out at me.
However, I don’t think that is how it works. If you commit hostile actions towards someone and withdraw removing the threat, you cannot be shot in self defense.
But if you return and come at the person, pounding on the door shouting threats like “I’m gonna kick your ass” that is a “new” situation and is not tied to the old one of throwing an iPad at someone, who retreats and comes back.
If charged, that will probably be the defense. I wouldn’t want my freedom dependent on it being a new situation. Not much information here, but it’s tough to excuse firing through the door unless a real effort to break the door down was present, preferably on video. My guess police aren’t waiting because of stand your ground, rather to decide just what to charge her with.