SIBLING RIGHTS

I have a different situation here. Three years ago my niece passed away and I was contacted by DCF to take in her children, ages 3, 6 and 13. I agreed and the girls where placed with me. After placement, things started to be revealed about the youngest girls father and things he had done to them sexually. Since then I have adopted two of them. The 6 yr olds father has been fighting from the beginning for custody but cannot abide by the rules and has a no contact order in place. 2 years ago another adult sister has come into the picture and claims she knew nothing about the younger sister and wants to adopt her. She had unsupervised visits for a short time until the child came back to me saying she talked to daddy and he was going to take her for ice cream. Visits went to supervised for a year. Now that she is back to unsupervised, the child is very defiant and tells everyone that I am not her mother and just her aunt and that she does not have to listen to me. She refuses to do anything I ask or obey the house rules. When she comes home from a visit she has new clothes, shoes, toys and candy. She than teases the others that she gets new things and they don't. The adult sister has failed 2 DCF home studies and has now hired a private attorney and has had another private home study done and approved. She continues to harass me about everything. She has call child protective services multiple times, they come out to investigate and find the claims unfounded. Everything from dirty fingernails to a bruise from playing on monkey bars. The child comes to me and tells me things her sister has told her about not liking me and that she is going to adopt her so she don't have to listen to me. We have a hearing coming up for change of placement. Everyone keeps telling me not to worry because I have had her for 3 years, have adopted her two sisters and want to adopt her as well. I have to bring her to the hearing so that the judge can talk to her in private. Is it possible the judge will remove her from me and place her with the sister after all this time? I promised my niece I would take care and protect her daughters forever before she passed. What are yall's opinions on the situation?