Where Is The Door I Need An Exit?

I could write a book, but I will be brief. I am the mother of a 24 yr old daughter. My daughter's drug of choice is a speed ball(heroine and crack). I have supported and paid for countless rehab programs. None which were effective. She does not want to quit. She comes home to recover from weeks of drug use. When she is not under the influence of drugs, she is a decent mother to her 4yr old son. He has lived with me since birth. But recently, she has started threating to take him with her, out in the streets, if I don't give her money. I really don't know what to do. I give her the money just to leave him alone. I have tried to shield him from her addiction so he is unaware of the danger. I feel like Alice in wonderland, I need an exit to protect my grandson and myself. Help
Could you take her to court to get full custody of your grandson? Given her track record with rehab you likely have a strong case - this way you are legally protected and so is he. Legal Aid (Lawhelp.org) may be able to help you if the cost of a lawyer is an issue.