As she believed it was her apartment, I don't think her not following police protocol show a strong pre-dispostion to shoot somebody based on any excuse.
Thanks for the reminder. I am aware of the social media posts in general terms.
Showing a mental pre-disposition involves mind reading to a degree. As a result, I would look for direct indications of pre-disposition to shoot someone based on any excuse.
In short, I would want to see direct social media posts advocating pre-emptive shootings of suspects, political extremism of any orientation, racist ideology etc.
Or, I would want to see direct actions such as known to put out bait, then wait for car burglars, known to go on off duty trawling “patrols” on vague articulation etc.