Please help.A close friend has been a victim of abuse for 12 years I need advice on proper course of action

I have a close friend who has been in the custody of her aunt and uncle since she was 5 years old.She is currently 17 and has been physically and mentally abused for the duration of that time.CPS has been called multiple times and have failed to investigate properly or listen to the details of any incident from my friend's perspective.She is now beyond hoping for CPS to help her out of the situation and now wishes to go forward with criminal charges against both her aunt and uncle.What are the steps needed in order to go through with this?What kind of evidence or testimony does she need in order to better her chances of a conviction? Please help as soon as possible - Is this your question? Add additional information