You are under no legal obligation to incriminate yourself.  Not in a court of law, not in an interrogation room.  She killed the man in self-defense--which is not a crime--and if talking to the police would incriminate her--and it always does--she is under no obligation to do so.  Of course, she was acquitted.  If her election took place in modern times, killing her attacker would win her a lot of votes in certain constituencies.

This being said, if I were forced to kill an attacker, I'd be a basket case, and I can certainly understand it haunting her.  Morality play; no supernatural elements.