Mortal Thoughts

I just watched it on Tubi. I thought it was great. I love films with unexpected twists and turns. Maybe Cindy slit James throat but she did it to defend herself from getting raped. However, Joyce decided not to take him to the hospital. She killed him by letting him bleed out and not getting him help. I am confused about who killed Cindy’s husband. Was it Joyce because Cindy told him about what happened but said that it was Joyce who slit Jimmy’s throat. Was she afraid that he would go to the cops and then the truth about her not getting Jimmy help would come out? Cindy was only guilty of helping to dispose of a corpse.She cut him in self-defense and then wanted to get him help.