She could make any shot. It was why she had gotten so far in the army. If she could get stationary, she could aim as far as the bullet would reach. With short distances, she didn't even have to stop moving. It was why she had kept Moriarty's attention for so long. She had a knack for killing.
With John, that knack wasn't held in the limelight. Jim's focus was always on her last shot. John's was on her last wound. With Jim she took care of herself. Around John, she didn't always have to. It was different, but after Jim's death, it was nice. It kept her from falling apart.
The knack was still there, and she still found jobs to keep her skills sharp. But she wasn't praised anymore. If anything, John elected to forget that she shot people when she wasn't with him. It seemed that he always saw the good in her.
He had a knack for it.