Today my step daughter was trying to cut a water bottle with a steak knife. After I had told her that she was not to cut anything. She ended up cutting my step son on his arm. I was very upset because I knew something like this would happen that why i told her do not cut anything. My wife is upset with me because he got hurt on my watch and I understand. How am I suppose to do anything about it. If i had already to her no to cutting anything and she went behind my back anyways to do it. Need some advice. Any thoughts?