8yr old boy abusing his mother.

DS was raised in a home of verbal and emotional abuse by his father to his Mother, now the abuse has ended and he is gone, DS is doing the exact actions of his father to his mother. DS has been getting help from a Psychologist that excels in this field but its getting worse. DS is 8. DS showed none of this behaviour when his mother was living with his father, as soon as the DVO order was put on and his father had an access visit DS behaviour has slowly morphed into a horrid disrespect for his mother, calls her horrific names, destroys property. Mother is very distressed and does not know what to do, any suggestions would be appreciated. His mother tried to shelter and protect him that was her first priority but DS father did not care if he heard or saw all of the abuse.