K.R.
Dear C....you have a difficult problem...a common one in our day. Children often don't know their real parents and/or sometimes like the 'foster' parent more than the biological one.
Children cannot always express what they really feel. Sometimes they say what they think others want to hear...but it confuses them in side.
Often they 'hunger' for the missing parent...a sort of love/hate relationship. It is possible that she is even jealous of her little brother because he has BOTH parents. Her biological father has spread himself so thin that he cannot be a good father. His children are too spread around.
Don't think I am being mean...but children need on-the-spot parents. Todays moral situation is such that 'parents' are more like romancing teenagers. I heard a parent say today that they were still 'raising a 30 year old TEENAGER! It is a broken situation...and may be impossible to fix.
I don't know if the legal people involved would allow it...but I think the best thing for this child would be to establish her with your husband and the baby, and do your best to create a 'home'. If she is naughty, correct her...BUT DON'T YELL AT HER. Establish a few rules (NOT RIGID), in order to make some order for all of your lives. Always be constant with those rules...but don't let them become 'wars' between you.
We are 'spiritual' creatures...and often develop a 'spiteful' relationship with disobedient children. Control yourself. Show respect for both children...and use your words to create a fellowship between them. ("Brother LIKES/NEEDS you...your help.") And praise every instance of 'good' you see in them.
Use the same tactic with the boy. ( I know that this is hard when she is naughty to him...but you will think of ways to bring them together.) It will be up to you to BUILD (mend your broken one) a home...and all of you will enjoy the results. I pray that your husband will be helpful. Don't look back; make all of your steps be forward. You won't regret it.
I trust that you are taking them to Sunday School.
Bless your efforts...
KayMarie