Help Me

My 9 year old cousin lives with me and she is just about to drive me crazy!. She has a smart mouth on her and will dispute everything you say...i try my best to be patient with her because of her background, but i cant take much more.. She is always into things she has no business into! And always trying to be in adult conversations. She is rude and disrespectful and throws tantrums over everything possible. Please help me!!!

Do you moms have any suggestions for me?