International Adoptee Lost Original Paperwork And Wants To Get A Passport

Xposted on r/passport

My sister was adopted from another country at 6mo, at the time my parents got her an American passport and a permanent residence card under IR-3. Both have texhnically expired. A few years ago, an ex took a lot of her stuff when they broke up, including her folder of her original adoption information and passport. All we have is a copy of a birth certificate that is stampted as "not a valid proof of citizenship" and her expired residence card. She also has her social security card and driver's license.

What options (other than getting a lawyer) do we have for helping her get a passport?