Five years would not be a long wait to be adopted from foster care. These things are generally more in the hands of the judges than social workers. There are actually incentives to social workers in many states to get kids adopted from foster care.
There are some fairly standard procedures that are followed when a child is placed in foster care. If the child's parents die, and they have no relatives interested in taking the child, they could be eligible for adoption immediately. If the family she was with were approved foster parents, it would be a fairly quick process if they decided to adopt. Not that they would make that decision quickly, necessarily.
If the parents were just missing for some reason, and the child was a teenager, they might never become available for adoption before they aged out of the system. This is a very likely scenario.
There is a trend toward adopting children who have been in foster care, in some states, shortly before or just after they age out. The problem of terminating parental rights is passed and it's handled more like an adult adoption. This makes them a permanent part of the family and support through their college years.
Many kids just age out of foster care without ever being adopted , even if they stay with their foster families.
Look at the New Jersey DFSS site or New Jersey Adopt Us Kids for some state specific info.