Gonna be 5 years old. Attacking my 4 year old person

[Mechmonkey]

Okay so. I adopted two 4 year old cats when I was a single person. Since I had to rehome one of the two. Financial issues. It would have been both but... let's just get to the point "Boo" is not great at cohabitation with anyone but me. Boo was adopted from a family that had her well cared for, but she was indoor/outdoor. Since she has only been inside with me. I met someone with a 4 year old little person. And my "Boo" has been let's say less friendly to the little human than I'd like. Basically she polices her. Smacks at her, chases her, sometimes bites and hisses. Small person isn't going away. What do I do? 4 year old kids aren't going to stop running around and laughing.