The point is, if they are trying to portray her as someone with no survival training, your argument might make sense. "This is how normal people react when their car crashes in the middle of the desert." But in this case, they were clearly attempting to portray her as somewhat savvy about survival, or at least imply that she was not panicking; she had the presence of mind to take the mirror from the crashed car, and she stacked up stones to leave a trail for others to find. (Since nobody knew she was out there, leaving the car and trying to find a road did make sense.) Why, then, do they think it is more impressive to have her stumbling around in the midday desert sun, when they could have made it even more dramatic by having her find shelter, wait for evening or nightfall, and then (just a suggestion) make her way toward the lights on the highway, or even take an active role in the eventual rescue (instead of being found by a one-in-a-million fluke)?

I think it's just laziness, or perhaps they don't have a very high regard for their viewers' intelligence.