Oh My Half-sister... I Need Advice Please

So one day I was on Facebook and my dad was making dinner.All the sudden I get this message.. It said "Im your sister, my mom just told me, its on the bith certificate...we have the same dads different moms" I turn around and say " Is that true" He saids "possibly". I start crying. My dad tells me to block her so I do, then my mom comes home and she saids ok, it was good for you to block her." The next day I get up and go to school and my mom goes to work 4-8. My dad goes on MY facebook when she leaves and starts talking to her...! I see her calling him " Daddy," and Im in shock. I tell my mom when she comes home and everyone gets in a big argument. She ends up coming up the next weekend and we go to a hotel me and my dad and her while my mom stays home with my little sister. She sits on the bed with him and starts sucking her thumb and holding her blanket and shes 14!!! It seems like he loved her more then my just because they didnt see eachother for 13 years!! One day we got into a big fight like clothes everywhere and yelling and screaming. It seems like Im gonna get punished because she started the whole thing! I dont think its fair and im thinking about moving my room away from her.. Is that ok or is there any other advice??? She ripped my family apart and somedays I wish I never met her, at least not untill we were adults!!  Thanks!! :)