I don't want her to move in!?

Okay so my cousion wants to move into my house and I really don't want her to. Okay so 1: she's so mean 2: she steals my friends (I'm not een kidding even right now she's with her) and 3: she just annoys me . My mom under stands but my dads making me look like the bad guy. He just yelled at me to shut up and I'm a lier. I don't know what to do I'm just tired of it. I would rather live my friend. Please help what should I do?