“I live in NJ and one year ago I was granted full legal custody of my child’s 17 year old friend. She has now turned 18 and is a high school senior. Am I still legally responsible for her? Or does it terminate on it’s own? If so, at what point does this happen? Do I have to go through any legal channels to dissolve my responsibilities?”
It’s more what the child needs to do. In New Jersey reaching the age of majority (18) does not necessarily take you off the hook on the parental responsibilities you undertook. Such action on the part of the child to emancipate might be: Completion of college, Marriage, establishing a residence outside your home, entry into the armed services, the child becoming fully employed. I am not aware of anything you need to file, per se.