Youth pastor adopting a girl?

I am a 38 year old male youth pastor, never married. I have a 13 year old girl in my youth group whose mother doesn't want her. Her father, who lives out of the area, doesn't want her, either (because she isn't a boy). I have known her for about 4 years, and during this time her mother has talked about signing custody away numerous times. About 3 weeks ago, she asked me if I would adopt her. I was totally floored by this. She told me that I have been more like a dad to her than anyone else in her life. I had no idea she looked up to me this much. Although I do love her tremendously and would be thrilled to be her dad, the situation rasises some obvious questions. What are the chances of this even happening? Does it make a difference if the mother signs custody over to me (which I've been told that she would do)? Does the fact that this girl wants me to adopt her make a difference? I know that this would be a major change in my life, and in hers as well. Although I've had a lot of experience with teen girls from 12+ years of youth ministry, I know actually raising a daughter would be much different. I've already thought about medical care, schooling, etc. and I have a lot of female friends who I know I could count on. They're already a big help when I need them. I haven't decided for sure what I would do, but I'd like to know more about this before I decide if I need to proceed further. Any input on this would be greatly appreciated. Thanks!