There is something upsetting her as she is acting out perhaps if you seperate he children so they cant fight a lot may help, do not let her be the aggressor , when she starts to fight put her into time out, and make sure her older brother treats her kindly also. Are there any other children at her Fathers house, and has he got a new partner,perhaps there are other factors going on to upset her.
She has an older brother with Aspergers. I am the only parent here anyway, she does see her father- Tues, Thurs and every other weekend. Her and her brother fight non-stop but shes more the aggressor...
How does she get on with her brother is he older ot younger than her, if he is older is he kind to her, some big siblings like to tease the younger children. Are you the only caregiver?