Because she is physically harming another child, I would take her to your pediatrician and describe what you have described here. I also would not ever leave your son alone with her. Little ones hit and bite, but what you are describing sounds like it may be something that needs addressed with the help of a medical professional. If it is something she can control, you'll benefit from knowing that. And if it isn't, it will be good to have started early n the path to determining the cause and what remedies will work best for her.
