Read the book of Proverbs and get some insights on how the Lord wants us to live our life. It tells us in detail what will happen to us if we go in the direction you are going.
Lord please deliver this child of yours from that evil addiction they have. May they get into your word to see how your children should live their lifes'. Give them the strength to stay away from it all, and search you in your word to get the strength needed to avoid that kind of life. I ask in Jesus name amen!