I feel uncomfortable in my boyfriends home and refuse to go back there
Why are you uncomfortable in your boyfriends home?
I can't stand his sister.  I find her annoying.
That's too bad.  It is okay to not like your boyfriend's sibling.
I hate her. I'm going to sabotage her life by talking bad about her, which is going to make my boyfriend mad.
While you don't have to get along with everyone, you definitely have the choice in keeping the relationship amicable. Don't you want to be happy with your boyfriend? How about just ignoring his sister instead, so there won't be any drama?