How do you get over living with a girl that is having your brothers child and you cant stand her?

I live at home with my dad and step mother my 4 kids and 2 of my brothers and their girl friends. i have always felt that i am not good enough in any ones eyes. Now when this girl First moved in i thought i liked her she seemed real nice but that lasted like 2 or 3 weeks. Her and her sister got into a fight and started to drag everyone into it ie. my brother and cousin well i talk to my cousin and told him to not let there fight get between you and my brother. He seemed to be listening to me well then i went to talk to my brother well i called him into my room to talk to him and me and him were talking fine well i guess she didn't like the fat that i said what they were fighting over was stupid and that the boys didn't need to get into it. Well then she came into my room and started to yell at me i am 33 years old and she is 18 so i told her not to yell at me.. that did not work so again i told her to not yell at me or get out of my room....she was still yelling at me and again i told her to get out of my room....well she would not get out so i went at her cause i was going to get her out of my room and shut my door i do not hit people well before i could get in her face to scream at her to get out or i would move her out my brother got in my face between us and started to yell at me and she was still yelling at me and still in my room well like i min later she left and went in the hallway in front f my brothers room and was still yelling and called me some names then i said you need to leave and get out of this house.. then me and my brother went down stairs and were yelling and my dad told me to go up stairs nd he would deal with it well i am not all sure what was beaning said but the next thing i know my little girl came home from school and when she came up the stairs his girlfriend was going down the stairs my girl said her name and started to run back but i need to talk to her and then his girl friend yell so not so nice stuff about a daughter and then i started to yell back and ten my dad yelled up stairs and she yelled at my dad and it just got ugly from there well my dad wants her to leave but my stepmother does not want her to leave cause it would make my brother not happy (wow i just love where i stand in this family) so she got to stay. i don't deal with stress very well and got myself put in the hospital cause i could not breath. well after i came home i started my cleaning day a few days later was cleaning everything up and when i mop the floors i always lock the door so i poked my head in the garage to tell her i ws locking the door like i always do well i locked the door and went on moping my floors well then i see her walking around to the back door she comes in turned my music off an i know she was calling my brother the next thing i know i am getting a call from my stepmother saying you cant lock her out she is having a baby i told her i didn't lock her out she could always go around like she did. well after i got off the phone with her i was not going to clean anything else anymore so i went out on the front porch and was crying talking on the phone to my friend telling her what was going on and my brother pull up in his car gets out and starts to yell that if i kill hiss baby cause she is stressed out cause of me he is going to punch me in my face well we start to yell back and forth it gets real bad ten he locked me out of the house and when he opened the door i pushed him and we yelled more and we were in each others face and then he pushed me out the door and i fell. then the other brother that lives with us stepped edd in and the fought i really don't know what to do anymore my dad wants the girl gone and i hate her and fell like i have lost my brother forever but i don't know what to do anymore i am so sad i want to die i don't want to leave my room i have sent my kids away cause i am scared i will do something to hurt myself to stop all the pain please help i love my family and don't want to lose them but i feel like i am losing everyone of them