My son went to prison for two years for getting addicted to pain pills. His girlfriend at the time took care of her. She even went as far as getting temporary custody of her behind the families back. We thought our grandchild was in a good environment but my son was recently released and the old girlfriend is really mad and hates my son even tried to put a year restraining order on him which was dismissed by the judge. My son had no violence anything the whole time they were together. She has turned our granddaughter against her dad to the point she doesn't want to see him. I don't think this is healthy, because when our granddaughter is around us she tells us how much she loves her dad. I just think she should come stay with us so her and her dad can heal.

Is this ex girlfriend the mother of the child?

Is the child fed, clothed, medicial needs taken care of.

Just merely one parent hating the other, is not grounds for you to get custody.
She should have gotten custody of child, if child is with her and father not living there. That is the correct procedure.

The father would have the right to try and get custody, if he can prove child beter with him.

If mother trying to turn child against him, that is an issue he needs to take to court, and address with his visitation rights.

If the girlfriend is not biologically related to the child, go to court and have custody transferred back to your son or yourselves. I would strongly suggest getting an attorney. You need to review how she got custody in the first place.