adopting a foster child

I am a resident of Tn but the child I wish to adopt is in Ms...She is the foster child of a family friend of ours. She has been with them for two years almost and the parents rights have still not been relinquished which makes no since to me because the mother doesnt even try to get her back. and the time that she did try right after they were taken she failed again, I dont understand why they dont just claim her unfit and let the child go up for adoption. Anyways I was wondering if anyone knew what I might do so that the state knows how badly I want to make her my child and give her a good stable home..Any advice??