I agree that this is a plausible theory, although your second version is the only one I think makes sense. She was within view of the RV and truck (according to RT, see the discussion where
@cazador contacts the Colorado River SBCSO division and gets the GPS coordinates for where RT says Barbara was last seen).
I do believe it's possible she could have headed east rather than north at that trail intersection, but in that case, she was very confused, perhaps already in an early phase of heat exhaustion. While the area was thoroughly searched, she would have intersected the road about a mile away from the 5th wheel. Not seeing the 5th wheel, instead of retracing her steps, she must have walked someplace else. There's no trail immediate opposite the place where the eastbound trail intersects the road, so it's anyone's guess what she would have done next - but if she desired not to walk in her bikini along Kelbaker (for safety and other reasons), she might have tried walking off road on the other side of Kelbaker - but now 1 mile from where she should have been.
I've long thought that the search focused too closely on the side of the road opposite where the RV/truck were. There are photos from several days of the search, only one shows the northern side of the road being searched. In that photo, searchers are shown walking along the dirt road that begins near where they were parked. It's a vast area to search. Helicopters are pictured searching to the south, but not to the north.
Personally, I want to go out there to look around, and actually had a plan to do so last February, but COVID became a thing. I wish someone could have organized a drone search on that side, preferably in 2019.
The symptoms of heat exhaustion, leading to heat stroke, are subtle but definitely include confusion.