Step-daughter wants to run away from her Father's home.?

My wife and I are going through a divorce and we are already living apart. My step-daughter, including my wife, blames my wife completely for the divorce. As a result, my step-daughter (15 years-old) no longer wants to live with her mother and her mother doesn't want her in her house either. She is currently staying at her grandfather's house (where her father lives). She has always hated living there and hates her father almost as much as her mother. She refuses to live with either of them any longer and is contemplating suicide if she can't find a way out. Neither of her parents are willing to let her just leave and live with someone else, including myself. I told her that I would try to find out if there were any options for her short of living on the streets if she could hang in there a little longer. But in reality, I just don't know what I can do for her. I really do fear that she will hurt herself if she can't leave that house. What can I do for her legally if her parents refuse to give any consent? I thought about calling Social Services, but I read in their website that they only deal with neglected or abused children. She wants to live with anyone on my side of the family, but I don't think she can legally choose to do that.