I have a really hard riddle , can you tell me what the answer is ?!?

So a widow is talking to her therapist. She is telling how her husband died. She says he was watching a movie about a beast and in his dreams he was dreaming that he was being chased by a puma. He turned so violently that he had a heart attack and died in his sleep. The therapist knew something she said was fishy and sent her to jail. How did the therapist know the widow killed her husband?