Am I being unreasonable about my housemate?

[Rachel]

This may be a typical housemate problem, but in my apartment, my housemates seem to do whatever they like without giving any notice. One housemate has a couple of friends over for visits every so often - they are very noisy, but are pleasant and I don't really mind that. She also has invited large groups of people back to our apartment at 2am after being at the nightclub where they shout all the time and wake us up as well as leaving a mess in our kitchen/living room. However, this is occasional and I don't really mind as it is her house too.

The housemate in question, however, seems to be the one having a problem - but with me.
I had my boyfriend over for one night a couple of weeks ago and she lost the plot. She rang her parents and basically implied that I was a slut and she was scared of him being in the house. The next morning she confronted us and complained that she didn't want him over because she "didn't know him". She had her on-off boyfriend over for the previous week without informing us and he was there 24 hours a day. He was rude to me as well as her and was lazy. She had told me prior to that after they broke up yet again that he was not a nice person at all. I had never met him before, but I didn't complain because I had my boyfriend to visit sometimes. I assumed it would be okay for him to stay without asking in advance as it was an unforeseen problem that he wouldn't be able to get home. She has known my boyfriend for a good while - he has always been friendly to her, even helped her out with some information she needed for assignments and was never a slob if he came for a visit some evenings and would leave again after an hour or two. He always helped me to clean the house (I always seemed to be the only one to do it) and was polite to my housemates. We have a fixed rent as we are staying in student accommodation and we are allowed to have guests to stay a couple of nights according to our lease, so he is not entitled to contribute.

So she essentially said he could come over less often but we were to stay in my room. He didn't even come that often anyway. Then she rang me at 4am one night and woke me up asking me to walk a couple of miles to a house she ended up in with some guy after a night out and she wanted to go home but she was scared she would get kidnapped or stabbed or something. She was asking me to make the same journey alone and bring her back. I actually got up, got dressed and got her. She never appreciated it.

She never cleans up after herself and then complains the house is dirty so I have stopped doing every one else's chores, I only do my own now. I am almost afraid to sneeze in my house because I don't want to annoy her because she complained that I was noisy when I accidentally dropped a pot in the kitchen one day making dinner. I am so careful not to make noise, not to get in anyone's way. I stay in my room most of the time now and my boyfriend has only been to visit once since and we stayed in my room. She gives out how she has assignments and study to do, but all I see her do is skip college, lie about in her pyjamas all day and watch movies, post on Facebook about her great days of shopping and lunch with her friends and overdrafting her bank account..

Am I being unreasonable about this and am I in the wrong initially for having my boyfriend over to visit and stay one night? It's driving me insane..
She did "wrong" what I did and more and I never complained..

I guess for the next college year I will have to ask my parents if I can live somewhere with no housemates because I feel so uncomfortable and paranoid.
I appreciate the idea of the agreement, but at this stage it may be a bit too late seeing as I will be out of there in two months time for summer? She has laid down the law already and I'm the kind of person who adheres to people's requests.