I personally think both knew.
Interesting thoughts. Have wondered about some of the same myself but not all.
However, on this one, if she was hoping to be picked up, then why not just confess when confronted with her lies? If she would have been pulled over and confessed say in another town, why not just go to a PD in another town if she did not trust the one. Heck she could have went and confessed to Las Vegas PD and begged for protection before going home. This woman's actions do not fit someone scared and doing the right thing. The trip to Vegas, Sonic, etc. The burning of all of these phones, Kelsey's, the burner phone, etc., pretty convenient they are gone.
I find Colorado Springs odd too in some of this. I also find it odd that some reports say he and his bro are estranged and yet he talked to him prior to talking to police was it? I do not know the area though so could there have been a logistical reason for that department?
I wonder myself about some of your points and not so sure on others. However, all are food for thought...
I so far see her as guilty as he is but reserve the right to change my opinion as we learn more. And certainly respect your opinion and everyone else's. For some reason, I keep feeling like I am watching an R rated version of "Dallas" even though it took place in the wrong state...

jmo.