Surely fatal without it.

Damn those pesky gubmint regulations !

Seat belts (far cheaper) were already required to be installed in cars. The problem is that we couldn't be sure people would use them. (Even automatic systems were being defeated.) Most lives saved with air bags would also be saved with seat belts, if people would use them. So then it is actually a worthwhile question to consider, how far the government should go to protect people from their own stupidity. Arguably, lots of people (those willing to strap their own seat belts) had to pay $500 or whatever for almost no benefit, except to protect people unwilling to strap their own belts. Then ironically, with the Takata disaster, many of the airbags didn't work properly anyway.

She drove through a guard rail?

The sky did fall.

She was very lucky.