6 year old daughter help

My daughter is 6 years old and I'm really trying my hardest with her but I just can't. She doesn't listen, and she's being so bad. If I'm putting her little brother to bed (2) she will hit him, kick him and scream at him. Bed times are very very hard with her. She screams and fights and hurts us, especially if I can't cuddle her because I'm taking care of her brother. I'm hiding in the bathroom now, it's so hard. Any advice?