Okay bro here what you gotta do
When the BF is at her house lie in wait in her bushes in front of her house and when hes leaving run by and clock him the jaw or eye whatever just rock him(of course wear a mask or something and some baggy clothing to avoid identification from him) and run as fast as you can to your friends car or cousin or whatever just someone that you know that has a car waiting at the end of the block or whatever and jump in and speed off.
Dont know how thats gunna help you and what not but maybe she'll dump him for being a pussay because you knocked him out
When you see him again be like omgwtfbbq and ask wtf happened to his face so he doesnt know its you
Also didnt i talk to you about this ingame? Or maybe that was someone else.