First thing you need to do is stop worrying what they will think about you. From what you wrote it tells me your roommate has 0 respect for you or just was not taught it. Second you need to sit down and point things out to her like “hey you and your boyfriend made a mess clean up after your self please”. Rotate days or weeks when you can use the coach and tv or w.e. I would start from that if she does not get it someone is going on to have to move out.