learn the lingo first boy. This is basic stuff. What are you expecting from a law firm?
She needs to get her Thai passport which she will use to enter and exit Thailand. US passport to exit and enter the US. You don’t need a lawyer for such things especially one in the US. They will just fleece you and not do anything
there is another group called ‘Thai Citizenship group’ they can answer all your questions. It’s not an uncommon situation at all. She needs to get her Thai ID card and passport as the first step. This group can explain everything