Except that whether she was reasonable in her expectation to be at her home is central to that question. If she was (she wasn't) then she could be expected to defend her home.
If her expectation was reasonable, which it wasn't.
We have to be careful not to forget we are only able to use the limited information we have at this time and base our judgements on that, so of course the below may alter when we here the evidence at the trial.
Now according to what we know the following happened.
She came home from work in her uniform with her gun loaded and stored as she would have when on duty.
She went to her apartment, we know she didn't but some argue going to the wrong address is a mistake many people could make. This is the "mistake of fact".
She (this is a point we have very little clarity) apparently found her door already opened.
She entered the apartment (thinking it is her apartment again the "mistake of fact")
She saw someone - no mistake here there was someone in the apartment
She at that point decided to kill that person - there is no mistake of fact in this decision
She drew her weapon - she did not think she was pulling out an unloaded gun or a taser so no mistake of fact in that action
She aimed - again no mistake or accident at this point, she did what she intended to do
She fired her gun - again no mistake or accident here, her finger didn't slip, she didn't stumble and accidentally fire her gun.
She aimed the gun - the same as above
She fired her gun - again no mistake, no accidental firing
This is why I keep saying the "mistake of fact" only gets her to the wrong apartment, it played no part in her decision to try and then succeed at killing Jean.