My Step-Sister Makes me her Personal Fuck Toy

So after the whole me catching her getting fucked by two guys in my Frat the other week [See Part 1 → “If My Step-Sister Can Get Tag-Teamed By Randoms She Can Fuck Me Too”], and me subsequently holding it over her head until she agreed to fuck me; she turns the tables. What I didn't know about my scheme is that she actually had a nanny cam recording the entire thing. So a few weeks later she texts me while I am in class saying that she has an emergency, and that I need to come right over. Being a good step-brother I leave class and head right over, but once I get there I see her in her favorite slutty outfit and completely fine. After some back and forth she explains to me that what I pulled on her actually made her realize that she needs to focus on school and not be out chasing dick every night. At first I am pretty smug knowing I helped her out in the big picture. I assume I am off the hook; wrong. She wants me to be available to fulfill her sexual needs, anytime she wants, any way she wants. Not only that but I have to move into her apartment so that I am at her beckon call whenever she needs anything. I try to refuse until she tells me about the video she has. I have to cave, So I make her cum like she asks, and then as a reward she lets me cum inside of her. I assumed it really was a reward, until she tells me that she never actually had an IUD. So now I just came inside of my own step-sister, and if I don't do everything she wants from here on out, she won't go get Plan B.