I think a child is being abused?

I have a concern about a child. She is in the Custody of someone I know, her mother gave her up when she was 9 months old because she was unable to care for her, well this person that I know has had Custody for 3 years and the mother of the Child does get to see her. But my concern is not with the real mother its with the person who has custody. The child is very distant, isolated, and depressed, she acts out states she does not want to go back home when I watch her for the person who has custody. She will cry when the person who has custody comes to pick her up, she has a fear of getting changed is there is another child around even when the child is 1 years old. The person who has custody of her will not let her see any other family members other than the ones that are court ordered to see the Child. The person who has custody was seen yelling at the child calling them a crybaby, and a brat. The person who has custody has also told the child that "you are always in my way" and "Get out of my A%%" The Child is in counseling but the person who has custody blames it on the Child's Real Mother, but the Child does not show fear of the mother its only the person who has custody. The Child will start crying for no reason, she will start crying and run if they spill something or get told no. The person who has custody blames the real mother for everything but I know other wise. What should I do. I know the person who has custody has always gotten their way with everything and gets away with everything. But I know whats really going on i see it all, The poor child needs helped but the person who has custody makes sure the real mother gets blamed for everything when its not her fault. People help ways to get this poor child away from the person with Custody.