Sanity over Family?

This post will be clearly not about me or my son.
I usually dont complain about family on here because I use this as a journal of my adventures in mommyhood.... (where have i heard that phrase before?)
Ive got a dilemma that I would (well wouldnt) like to share. But where else can I just get this off my chest.

My sister, lets call her Leach and her boyfriend, lets call him Toe Jam, have been living with my mother free of charge since my sister found out she was pregnant.
Now Toe Jam thought hed be all manly and take care of his "family" and get a job with my moms fiance. Which said fiance was happy to have him along.
While leach sat on her ass getting fatter, Toe Jam worked less and less and played more playstation, and talked to tons of awefully cute 14 year olds on myspace.
Now my mom and her fiance had their talks with Toe Jam about his laziness. They asked him to start picking up after himself, maybe go to work once in a while.
Which in turn he took as "attacks on him" and complained to Leach.
Leach decided long ago that my mother didnt love her and that it was her job to always buy her things and basically buy her love. Support her when she had no where to go, and mother always did.
Well anyway, today my mother had it and told Toe Jam to get out by the weekend. So Leach decides this means my mother wants her and the baby to die. She throws anything and everything she can find at my mom and her fiance then runs outside screaming "you hate me and my baby"
Now I said this little fit is just because my mom yelled at her boyfriend and her pride is hurt.
Leach was never told she had to leave, or that she wasnt loved.
These two "children" are ungreatful, lazy pieces of crap. If it wasnt for my mom feeling so responsible I would literally kill my sister.
My mother is caring and nurturing and always ready to put you up when you need to get on your feet. Thats exactly what she did for Leach and Toe. For too long.
If Leach wants to run away and live with Toe and his daddy, good for her. My mom will feel guilty and have to get over that. And sooner or later they will both get kicked out of there too. No one wants to let two ignorant lazy fools and their offspring (god knows how many innocent lives they will unintentionally bring into this world) live with them for long.
My poor mother is right this minute trying to have my call my sister and calm her down because she is in her room crying. Its tearing my mom apart to hear her cry and know she caused it.
I want to not call my sister. I want to kill my sister.
I hate her for what she puts my mother through and I hate her for bringing a baby into this world with someone just as lazy and retarded as she is. I hate her.