I've been driving for 15 years and have not had a single accident, despite not praying to their invisible friend. Does your co-worker thank her diety every day when she gets to work? Afterall, her tire could have gone flat and threw her off the road, her brakes could have gone out while she was in the middle of traffic, another car could have had a problem and smashed into her, etc. There's probably a million things that could go wrong every day. Does she assume that there were a million miracles?
By the way, there was a good discussion on the problems of miracles with a Christian caller on last week's episode of The Atheist Experience:
The part about miracles starts at the 10 minute mark, but the whole clip is worth watching if you haven't already seen it. By the way, the reason that they think it is a prank call at the beginning is because Tracie had literally just spent 20 minutes debunking the claim that atheists hate God before the caller came on and made that assertion.
I think it'd be more appropriate for her to thank the highway engineer who designed the road or the driver of the salter truck that gave her just a bit more traction.... or the driving instructor who taught her how to drive out of a skid.
If she's going around thanking people, then not thanking the people actually responsible for her good fortune seems a bit ungrateful to me.