2013 Nissan Altima seat belts problems

My wife's vehicle was stopped on I-95 about a car length behind a minivan that had also stopped for debris in the road, a toyota pickup truck hit the rear of her car at speeds in excess of 60MPH pushing her car into the minivan in front of her at a speed of at least 30MPH, the SRS airbag in her car failed to deploy and quite possibly the seatbelt as well. My wife struck her head on the vehicle's left side roof support beam and suffered a concussion, whiplash and other lesser degree injuries as a result.

The day I purchased the vehicle (1/23/13) the seat belt light would not shut off. The passenger airbag light would also indicate that the passenger airbag was disengaged with a passenger in the vehicle. The dealership (rosenthal nissan of tysons) took the car in back and made some adjustments. The problem apparently went away. Tonight (2/9/13) the passenger airbag sensor once again indicated no passenger when my 110 lb wife was sitting in the seat. I tried it with myself (175lb) and again it occurred.