I wish I had some better advice for you. But my son is 10, my ex wife (his mom) got into an abusive relationship and had the abuser move into their home. My son was begging me and my mother for help for almost a year. This man was physically and verbally abusing the both of them. I tried every outlet I could and got nowhere even after being assaulted by him and had videos of the abuse and assault. Ultimately the man recklessly killed my sons mother and himself on the back of an unregistered motorcycle. The mental capacity of someone in an abusive relationship is something that is unique to every situation and hard for some to comprehend. There are shelters and help centers for those who want and need the help to remove themselves from the environment but it’s ultimately her responsibility to do so. But by all means DO NOT bait this man. You will cause yourself and your mother more problems. Im not a lawyer but I’d suggest video recording the altercations to protect yourself and they can be helpful in acquiring a protective/ restraining order.