Trouble with younger sister! help me?

I am 14 years old, my parents separated when I was 2 years so I never knew what it was like having a family, at the same time my father got a girlfriend who was until today, in 2008 they had a daughter, they waited 11 years of my life to give me a sister, seriously? I am outraged at this, when I was younger always said he wanted to have a sister, to play, but not now, now my sister is 3 years old and I'm 14, that is when I'm 30 she'll have 20, etc., that is horrible! i don't wanna be a role model, who wants that? -.- and she don't do nothing that people say to her, NOTHING, she implies with everything,if you told her she can't do this she does that