It bothered her more than she could adequately express that she was still haunted by Oliver's death so many years after the fact. She had killed plenty of others that didn't creep up into her nightmares when she closed her eyes. Maybe the reasoning was simply because it was the first life she had taken. It was the moment that she knew she could not go back to being the same Hermione Granger she had been before Harry was killed. If she had refused to kill Oliver, Antonin would have either killed her himself or dragged her to the feet of the Dark Lord. She had a choice. Her life or Oliver's. To choose hers over his had been selfish and a line had been drawn in the dust that she'd not hesitated to step over.