Air Bag Light On problems of the 2013 Buick Encore

Purchased a used 2013 Buick Encore with 21,115 miles. After two (2) months the passenger airbag light starting showing off when my wife was seated in the car, she weighs 110 lbs. It would come on then go off or not come on at all. Took car to nearby dealership, they stated "no problem, we can adjust the sensor all the way down to 85 lbs. " about half way home the passenger airbag off light came back on. After six (6) trips back to the dealership, which included replacing the seat sensor and the passenger presence module, the assistant service manager hooked up a computer to the car with my wife in the seat and the airbag light off. He said the computer was showing the seat occupied but the airbag disabled. He then stated he would have to keep the car and talk to the engineers at detroit. The next day I received a call from the service dept. Saying my wife would have to weigh 125 lbs before the airbag sensor would activate and it was normal for the airbag to be off and that it would actually be better for my wife if it the airbag didn't work. I find this totally unacceptable.