It is simply highly improbable that Amber Guyger did not realise that she was not in her apartment before she shot Botham. Based on the videos of the layout of furniture and other equipment in her apartment and Botham's and that his 50 inch TV was on she would have to see that she was in the wrong apartment.
As soon as she opened the door, with the 50 inch tv on, there would be sufficient lighting to recognise the living room area was not hers.
As soon as she opened the door, with the 50 inch tv on, there would be sufficient lighting to recognise the living room area was not hers.