Process After Getting Immigrant Visa

Question details

My mother is currently in the US. She entered based on the Immigration Visa on her passport and gave the sealed packet at the port of entry. We went to to the SSN office but were told that we need to wait for the SSN to come (via mail? - they had no clue). She wants to leave in the next few weeks. Questions:
1. Can she reenter without a physical GC in hand? She was told it takes 6-8 months to come at port of entry.
2. How do we get her SSN? Is it mailed automatically?
3. What else should I be aware of before she leaves the US?

ANSWER

Make an infopass appointment and get her passport stamped for temporary proof of green card. She can travel with that. Normally, the physical GC takes just a few weeks. I am not concerned about SSN. That will arrive eventually. But do review my blog videos about I-131 and maintaining green card, etc.