At the end when Brenda picks up the cat, we hear the sound of a hiss, but the cat's posture is not a defensive one or showing any adverse reaction to being lifted and handled; in fact, its pose shows submission, not a situation that would elicit a hiss.
The actor who played Nick Coslov, Seth Gabel, is 5'10" but according to the story the killer is suppose to be 6' or taller.
In Russian, PetroVNA is a patronymic, namely the daughter of Petr. The correct surname must be PetrOVA.