Three years ago, the girl who was homeschooled told a teacher who she saw once a week that her stepmother was locking her in her room and only giving her two pieces of toast a day, The Seattle Times reported Wednesday.
The girl remained in the home for three more years, the newspaper reported.
In August, officials responded to the home after a neighbor heard screams. Authorities found the girl, who weighed 48 pounds and suffered from dehydration so severe all of her teeth were rotting.
"Obviously we wish we'd had the vision to know that something was going to happen to this child," Children's Administration head Cheryl Stephani said.
"We're going to thoroughly review the case and see if there were things that were not disclosed at that point (three years ago)" Children's Administration spokesman Thomas Shapley said.
On Monday, the girl's stepmother, Rebecca Long, and father, Jon Pomeroy, were charged with criminal mistreatment.