What you wrote the casework said makes sense. If a baby is born addicted there are a couple of ways of dealing with the issue. One is to not give any drugs to the baby and see if the baby's body is able to be drug free by itself . The other (or if the baby's body is not capable in a short time) is to give the baby drugs (the drugs, or combination of drugs, depends on what substance, or substances, the mother was addict to) in a decreasing way.
Both methods have withdrawal. But it may be less severe (I'm guessing here, I do not know for sure), if the baby is given some drugs in a decreasing way. Despite is all, she is a lucky baby. Some babies need six months on drugs. She is also lucky because she has you and your family.
I'm sorry you were only told yesterday that there will be no funeral for your dad. Maybe you will be able to attend the family get together.
Sometimes good things fall apart so better things can fall together. (Marilyn Monroe)