So my sister and I have been best friends for a majority of our lives. We are only 18 months apart and are roomates. Im going to try and tell this as unbiased as possible. My sister has never liked ANY girl I have dated. Sometimes warranted, most not. As a result she doesnt like my current girlfriend either. I met this girl about 5 months ago and we really hit it off. She is absolutely awesome and we honestly have never had that first fight. She has never given my sister a reason to not like her. Always been very friendly and nice. Anyways my sister really doesnt like this girl. Slowly she has been starting to stay over my place more and more. So she stays at my place between 2-4 nights a week. Here lately its been more, strictly because I have been working 75 hours a week, and its been the only time we could spend with each other. About 2 weeks ago my sister confronted me and asked when she was going to start paying rent. This blew up into a HUGE fight. I texted her about 2 hours after it and told her that I understand that my gf stays over alot(the most ever was 4 nights in one week) and that we would try to limit that number as much as possible. She didnt respond to my text. So then I asked her to just talk to me about it. She didnt respond to that. So I texted her back again later and told her that she was being very immature about this and taking the wrong approach and that until she talks to me like an adult, I refuse to change what im doing. Her and I are currently talking but on a very limited basis. Am I wrong for thinking that I pay half of the rent so if I want my gf to stay the night a few times a week, she should not let that affect our relationship?