If you're worried about direct contact again (and I don't blame you!) I would definitely suggest writing a letter to the mother. I had some issues with neighbours a while ago (noise, but not assault) and they refused to speak to me or to answer the door to the council. I wrote them a really balanced, civil letter, not threatening them, but just asking for a solution that they go inside and be quieter after 11pm. I didn't get a peep out of them after that. Obviously here you are dealing with much more unpleasant behaviour, and I'm not sure you'll get the same miraculous response, but you at least have a good chance of putting your case to the adult in question without being threatened. Also follow up with the police and enlist James Barber's kind offer of help. You were assaulted, it's a criminal offence, and the person in question should be prosecuted. That in itself may deter at least some of the behaviour.