When I was 15 my best friend, my only friend at the time, confided in me that her father had molested her and her sister. She claimed that he changed, but later on said she feared he had begun doing those same things to her younger sister. I was torn. I felt that I should speak to our bishop and yet, I was her friend and the only person she told. I maintained her confidence for months, but it weighed on me heavily. After many months of struggling with it I finally decided to speak to the bishop. She stopped speaking to me after that, but even now I am certain that I did the right thing. There is a young girl who will not be harmed by her father any longer. It was by no means easy for me, I am quite shy by nature and I feared losing my only real friend. I realized though that I owed it to her and to her sister and be a true friend and do what she needed for me to do rather than what she wanted.
You don't have months to make that decision. You should speak to the people at the clinic and let them know she has a fake I.D. and is underage. Perhaps speak to her mother rather than her father if that's possible. Encourage her boyfriend to be supportive of her especially if her family turns on her. She may be upset with you for awhile, but someday she will be grateful to you for it. A young child will have the opportunity to have a happy and fulfilling life, and I firmly believe when she holds that child she will understand that you are indeed her friend. You and she both will regret it always if you do not do so.
Anways take care and may the Lord bless you and give you the strength you need. Im pulling for ya =)