What a terrible situation for all...so sorry you are in this position.

For what it's worth...I believe there is a child being abused in this situation. A 15 year old is still a child legally, emotionally, mentally and even physically. You are right, this man is in a position of control over her and power, and I believe she is in real danger. As hard as it may seem, I don't think you have option to "butt out"...this child needs help and unfortunately you're the one who is in a position to make sure that those who can help know that she needs it.

Best of luck to you - you're in my thoughts.