custody of child not ours

[leannrf]

just wondering how hard it would be to obtain custody of a friends child the mother is 18 and no father known of and grandparents drug users we have he child at least 5 days and nights a week when the mother has her she just takes to someone else but she won't sign her over she has told people that would make her look bad we have had this child since birth and she is just turning 2 and we live in arkansas could someone please give me some advice thanks leann