The article in the original post states that the girl is the US citizen’s sister and she is 19 years old. The article states “teen” to garner sympathy from readers, but to the US Government that means adult. She has no passport so her identity cannot be verified. The USC and “teen” sister should both get DNA tests to prove relationship, then USC should go back to USA and petition her. Unfortunately the nephew who is 16 needs a parent or sibling in the US with citizenship or a green card to petition him.