After talking with my father, to make sure I had his support, I talked with my sister. I don't think she is taking me seriously though.

I told things had to change and they were changing today. I then told her she is now responsible for half of everything such as rent and utilities. I also told her I want to be treated with respect and she wasn't allow to have any strangers over period and if she didn't like there's the door. She looked at me very calmly and said "fine, I'll move out." I said you have until the 1st to get out or I am calling the cops and reporting you for trespassing. I am not paying for her to move back to NH and I told her even though she didn't agree strangers were still not allowed in the apartment.

The fact that she looked at me calmly and said "fine, I'll move out" leads me to believe she doesn't think I am serious. I don't know if I can really have her arrested for trespassing because she's family, but she's not on my lease and I don't know any other way of forcefully eviciting her. As horrible as it's going to sound, advice on that would be appreciated.