About 15 years ago, my mother visit visa application was refused. During the interview, visa officer said that we could not verify your bank statement and it looks like you will not return to your home country. My mom did not understand what he is trying to say and what to answer. She thought he just wants to reject her application. So she did not try to challenge. Anyways her application was rejected but they did not give any letter that explains under which section. They just wrote 214b/P6C on the last page of her passport along with date received stamp.

Now I want to bring my mom to the US. She is still in our home country. Her I-130 has approved and I have submitted affidavit of support but have not submited DS-230.
Will there be any problem in visa interview?
Should I invlove any lawyer?
Can someone explain what does P6C mean?