My one year old daughter takes things from my 2 year old niece...?

also she hits and pushes and pulls on her, she is only 13 months old and my niece is 27months old but my daughter is so mean to her. She is the only child and doesn't like sharing. How can i break her of this "habbit"? i tell her no and pop her hand when she scratches and bites her but my baby just gets mad and screams, not cries but screams at my niece. My niece and her "FIGHT" about almost anything and its annoying. what should i do, and i know its normal for kids to fight over stuff but geez, my baby is MEAN about it! lol