Posession by another soul

My main character gets possessed by the soul of a girl who got reincarnated inside of her body. The soul happens to be that of a really *slutty*, fairly insane teenage girl, and when the girl takes over my main character, she causes my main character to sleep with people and get high and act out and all kinds of things like that, that she would have never done. The part I'm at has my main character being kidnapped by the gods, and when she is with the god of peace, she wills the soul to take over, because she herself doesn't want to get high with him (Yeah, the god is a hippie-like dude) and so the soul does, and then she causes the main character to give the guy *fellatio* (fancy word for oral sex x.x) and the main character is kind of just watching her body, from inside her body. She doesn't actually feel much, but she feels a little bit. It's drastically lessened. And my main character can hear, but it sounded muffled when the soul was in control. I want to develop the soul taking over her body thing so that eventually, the soul is reluctant to give my main character control of it, because the soul likes having a body of her own again. I would like to make my main character fight the soul for control of her body, but honestly, I have no clue how to write it. If you guys have ANY ideas on this, please comment on this forum. I NEED YOU!

Uh... I'd try intensish. It should switch between the perspectives of the MC and the alternate soul, just to make it interesting.