How fights can get brutal

Comments: "mother"/"my mother"/"mom"/"that woman" - whatever YOU call your mother has nothing to do with me. If I refer to her as something (e.g mother) and not as something else (e.g my mother/mom), that is my business, not yours. And no, I do not call her mother to her face, she is called "mom".

The day started off like normal. I'm told what to do and I do it. But then my mother leaves to see a movie and my sister "takes" the parenting position. First off, I won't mind that she does it, if she was good at it! Secondly, I'm older! Why does she think she can take that position, just because mother is out?

So now SHE is telling ME what to do! SHE has NO right to tell me what to do. Mother told me what to do and I did as mother said. SHE can't ADD on to what mother told me to do!

Mother told us not to be on the computer or watch tv until what we agreed upon was done (aka I was told to clean the kitchen). Anywho... Mother leaves, sister goes on computer (she is not done what was asked of her yet) and tells me I'm not done, so I'm not allowed to watch tv,

I ask her: "What am I missing?". And she lists a long list of things, that I had done, just not up to HER standers. They are however up to my mothers. I tell her she has got to be kidding me! And then ignore everything she says (childish, I know... but it works the best). She gets angry! Starts yelling at me about something to do with yesterday... I didn't go out drinking with my friends, and that apparently ruined her plans. So she is angry...

She then tells me to go to my room. WTF? She tells me because her plans were ruined I have to stay in my room all day, so that she can have the house to herself. WTF? How is any of this MY problem? Of course, I say NO! And she gets even more angry. She then tries to take my key (to my door) and I shove her away. She now so angry that her face is red, HITS ME! Punches me. Repetitively. And I push her away, which does nothing because her anger has to come out, and it's coming out in punches on me!

Mother is still at the movies and I now have a shitload of bruises... and one scratch mark. About an hour before mother comes home, she calls her. And tells her I started it. That I hit her first...

Oh yay, did I remember to tell you that she hates the fact that I'm alive? And she wishes that I stayed with my father, so mother and her would have a nice life here alone. She wishes that I didn't have money, friends, things or a family... To say those things to a person, who you have no idea what's going on with. You have NO right to say such things! I've considered suicide in the past, and saying such things aren't fun to hear.

Now I have no idea what to do... about my sister... or my relationship with my mother...