Is it normal to have crazy little sister

All my life my sister has been a complete bitch! Pulling my hair, throwing things at me and my parents, stealing things, lying about every thing, being abusive to our dogs, calling me names, and I'm 2 years older than she is, and 3 inches taller! She is absolutely insane! One time she pulled a huge knife on me and her pudgy guy friend! She tries to boss me around and intimidate me! She's way stronger than me and she doesn't just hit, she bites, claws, digs her nails into my skin, which my mom, my babysitter, and I all still have scars from. I can't fight back, what do I do? Please help! BTW don't leave comments telling me I'm a wimp!