1. the old expired passport (my mom got her new passport in 2008, before 2008, she used her old expired passport which has two B-2 visas); This time, she used her new passport, which also has one B-2 visa.
2. B-2 extension document: my mom never applied for B-2 extension in the U.S. Every time she went back to China within 6 months.
-Explain it to the VO if asked durng the interview.
So my mom just needs to take the old expired passport for the interview. Nothing else, right?
-Yes plus all the documents needed for the visa application such as new passport, photos, payment receipt, etc.