I don't feel safe at home..?

Okay so today my sister was threatening me with a knife and laughing. I have no idea what to do; I can't tell my parents. They never believe a word i say. She kept jerking it like she was about to throw it. She didn't actually do it, but i'm so scared that next time she will. She called me a cry baby and went up stairs. I don't know what to do; i told my friend and we're going to the consular tomorrow. i'm so scared ;/