I'd have water for drinking (some in a small cooler within arms reach for sure) and water in gallon jugs - for the car, perhaps, or splashing my face with, etc. I've never driven through the desert by myself - it can be very desolate in places (or it used to be).
Your comment about avoiding any cameras/video is a great point - and probably one of the reasons she brought so much gas with her from CA (and probably water, too - premeditation).
BUT...
I have a problem with this (meaning JA's story - not your theory!), and I take it a step further... back. To the house.
I absolutely do - not - see... and don't believe JA was not clean when she went through the house and left. It is completely ridiculous to think her hands were bloody (I suppose she could have put shoes on bloody feet, but I don't believe that).
There is only one small spot of blood on the washing machine - the rest of the house has no blood evidence. None. I think she removed bloody clothing in the bathroom, showered over Travis and somehow covered her feet until she could hit the clean carpet in the bedroom to get dressed. I think she did a load of towels and some clothing that had blood on them (because they were in the bathroom) - but covered them while carrying them with a clean item, then tossed the camera in and bleach to remove any blood.
Nothing can convince me she left that house, closing/locking doors behind her... while still light out - maybe nearing dusk -
with bloody hands and feet, in a daze (bloody clothes, too? Knife and gun?), drove *any* distance with bloody hands (stopped at a red light leaving the neighborhood - that would catch another driver's attention.
The dazed driving and suddenly seeing her hands and feet bloody somewhere in the desert and washing off with bottled water - is NOTHING but a way for her to avoid talking about what happened. Period.
Unfortunately, it seems she told Det. Flores an awful lot of
ninja hijinks that matched the forensics... indicating she absolutely knows what happened and isn't missing anything memory-wise, even though she was vague she was accurate -
she HAD to be to make the ninja story believable!!.
But - I'm just guessing too.

I don't think JA is ever going to explain things. So all we may ever have are theories with this. Grrr... frustrating.