I would think perhaps the son's bully is not a bad looking 18yo jock, and a cocky ass all through HS and the mother in her late 30s maybe 40ish hasn't had a man in a while. Her son would never think that it gets awful lonely for his mother around 40yo in her bed and has masturbated a lot with her own woman fantasies and needs. She didn't want to give in to this cocky ass bully, so it goes along the lines of reluctance as she's in such a vulnerable position, she becomes weak herself and her mature MILF pussy is hungry for a real man cock. Of cause her son's bully shows her a nice big rock-hard cock.