Zcorner119

Did she pay the $220 immigrant fee?

Since she has a stamped immigration visa that serves as a temporary I-551, she doesn’t need a green card for another 315 days. USCIS knows that so she is low priority.
 
Sign up for USPS Informed Delivery so that you get notice ahead of time that the green card is enroute.  On the day  it is due, set your camp, literally next to your mail box and wait for the carrier all day.  If the carrier comes and goes  without delivering the green card chase after the carrier.  A misdelivered green card is like a missing child. The first 24 hours matter the most.  

This is normal.  If she received her SS card, she will receive her Green card.....You have to be patient.  It can take 90 days. 

Just received an email from the NVC with case account information.  My online status also changed to "Case Was Sent to The DoS" 

She can come at any time before her visa expires.  She can come one week before it expires.  

Yes.
 
I would not risk it that close, if it was me.  With flight delays/cancellations, travel restrictions, etc, that week could leave your mom stranded someplace and not enter the US in time.  Maybe travel when there's a month left?  Whatever is best for your situation.