I already want to kill my roommate?

So I am rooming with this girl I met last year in college and she is a nice person, just very self involved. She was an only child and very spoiled. Still is. We are going to have suite mates. (basically we have four rooms all connected to a bathroom that 8 girls share. ewww i know) well we have all been trying to talk about the bathroom rules and cleaning and so on. My roommate is being so stubborn! For starters she is refusing to pitch in for any kind of soap, t-paper and cleaning supplies. She says everyone should worry about themselves and care their own soap and t-paper every time we go in to use the bathroom. Now I don't know about you but I don't always think to myself bring t-paper with you before you go in there. We are basically out voted her. I told her she could use her own stuff but don't touch ours if that is how she is going to be. Then she says well that is not fair. What if I need something? Now how does that make sense? She wont share her stuff but expects us to share ours with her? What that h*ll? What do we tell her. I told her no but she just laughed at me. I don't want to get all the girls to gang up on her but I don't know what else to do. Help!