In my novel, the foster child hasn't seen her parents since age 3. Now, at 15, how much would my protagonist know about her parents? Would she be told by her case worker? Any insight I greatly appreciate!
I used to work for Illinois DCFS. If you prefer her to know as little as possible about her birthparents you may have to rework a few things...
I would consider making her a) adopted from the foster care system, b) in relative care, or c) in a subsidized guardianship situation instead of a foster child. It's not likely a child these days would be in the foster care system for 12 years with no awareness of their birth family unless they have major special needs.
As a previous poster alluded to, unless parental rights were terminated early on in her life, she would have regular visits with her birth parents, and may have even been placed back with them on more than one occasion. And if parental rights were terminated early in her life, odds are she would have been adopted by now, either by a relative, or by a former foster family.
The exception to all of the above would be if your story is based in the 90's or earlier, when "permanancy planning" was not a big priority with kids in the system and they routinely stayed in foster care until the age of 18.
Another exception would be if she lived in a backwater state like Florida, which can't even keep track of the kids it has (it routinely "loses" them), much less find homes for them.
FYI, the case worker would have no choice but to tell her about her birth family, since its the case worker who would facility family visits.
Hope this is helpful,
Audrey