In need of opinions..or advice?

Hi everyone...I have some questions I hope someone can answer for me.

My fiancé’s sister is addicted to drugs.

She’s pregnant.

She recently went to the hospital because she was in premature labor and while she was there she tested positive for meth and weed. She has 2 other kids that have already been taken from her because of drugs.

We know the baby is going to be taken from her when it’s born. Can any of you tell me what happens to the baby after it’s born? Will it stay in the hospital until the drugs are out of the baby’s system? If one of us steps up and offers to take the baby in, does she still have rights to see the baby? Are we able to adopt the baby as our own? Just needing advice. We aren’t sure what we should do. We just want to help the baby the best we can..thank you in advance.