RT had a gallon of water in his backpack, so she'd have been headed toward him "for water." There was water in the trailer, which is where she was in fact headed. There are no other water sources out there. This wasn't her first time in the desert. She has lived out there for more than 15 years.
Practical is in the eye of the beholder. I don't find it useful to continue to declare Barbara "less than" in terms of her choices.
I totally agree with
@PaulR that the constant reiteration of what someone else would do in Barbara's situation and the implication that Barbara is wrong, ill-advised or even the subtle implication that she's unintelligent or reckless is victim shaming or even blaming.
It's my understanding that the neighbor's video shows both of them getting into the truck.
But more than that, LE says it has photographic evidence that she was where RT says she was, on the day she went missing.
No county in California is going to conduct an 8+ day search with aerial support unless they have reason to believe the person is out there. Plus, they had RT's phone (and last we heard, he was waiting to get it back). LE knows exactly where RT's phone was that day (and apparently, they stopped in along the route to pick up video).
Photos are never hearsay. We, the public, don't have to see them. Photos are physical evidence, whether they are printed on photo paper or displayed on a screen.