If the child is born and the baby is taken into foster care immediately from the hospital, the bio mom can suggest you as a placement, but that doesn't guarantee you as placement. The baby may be put with a licensed foster home until a home study can be done on you and your family. This could take months and you would not be allowed visits with the child as you are not the bio parent. She should make her wishes known to the judge, but that doesn't mean that you will get the baby.
If she does want to sign her rights away and have you to adopt the child, you need an attorney. Call and find out what your/her options are asap. PS-Do you want to adopt her child? What will your relationship be after the chidl is born? Are you good friends now? You may need some counseling in this area to make sure you are ready for this big decision.