Thanks.

I'd much rather pay for a new airbag than have someone in my car not get the advantage of an airbag because some foolish sensor isn't working... Luckily, the warning light came on and she brought it right back to the dealership (had just had service). They told her it's "rare" that the sensors fail, but that still seems ridiculous to me.

Any idea if the sensor can be turned off or overridden to keep the airbags active at all times?

Does the driver's seat have the same sensor? They replaced both seat covers and she was under the impression that they both have the sensors. Again, that wouldn't make sense - car can't drive itself, driver's airbag should always be on. I'm guessing maybe they just did both so the leather would match, even though she said it doesn't seem to match the back seat.