They should have taken her to Doc - I imagine looking at her teeth, bone structure or something would have provided some proof on an approximate age.
At some point they did take her to a doctor and it was determined that she was much older. That is why they had her birth certificate changed and left her behind when they went to Canada.
They knew she was an adult.
The woman then told the courts she was a child who was left behind by her parents and got them arrested. They have been trying to prove she was not only an adult but psycho.
I tell you what after this no one will want to adopt dwarfs.