I'm new here and need some help ASAP!?

About 13 years ago I adopted a little girl from an agency. You see my husband Mark and I are Christians and we are very deep in our faith, yet we have been unable to conceive so we decided to rescue a child. We finally decided on a newborn baby girl, Ariel, although I was skeptical. You see her mother was young and single. The adoption agency swore up and down that she came from a loving Christian family but I wondered how truthful this was. After all no good Christian would have premarital . But my husband convinced me we were doing the right thing by bringing this child into our proper loving environment and that she deserved to be raised right. We have always taken her to church and speak to her about our Lord; however last month she told me she didn't believe in God! Since then I have pulled her out of school-we now homeschool and only allow her to socialize at church. We have prayed for her and had our pastor talk to her. We can not get through to her. We have done everything right yet she still denies God. So the only logical conclusion is that her delisions stem from being born to an unholy and sinful woman. There is no other explination! So basically what I need to know is what to do. We can no longer have this un-Godly child living under our roof and infecting our other children with her nonsense. Since it is the fault of her birth mother and the agency (for insisting that she was a Christian) can we make them take her back and reimburse us for all of our expenses?