Lots of factors play into Will’s eventual journey of murders, but B did play a big role in snapping him in half. As for what she did, I wont go into detail, but if you can imagine a form of abuse, theres a 99% chance B has done it. I think the real kicker is Will would’ve been ok had he just stopped putting himself on such an egotistical pedestal and ask for help because of how badly he needed it.