Car 3 is not DW. Car 3 is not just anybody, but somebody who knew about the GPS. Who knew about the GPS in the car?
I'll take that a step further, "IF" car3 is someone that knew about the GPS, then they must know DV as she had JUST got the car. Otherwise a complete stranger that wanted either DV, the car, or both, stopped long enough to think about a GPS and disarmed it. But someone could have known she had gotten the car, could have known about her financing it, known about the GPS, known she wasn't at home that night but out celebrating, and known to follow her to the gas station. That's "IF" the person in car3 knew DV....I think the number of people that would know all that information would small. But maybe she told lots of people because she was super excited! And maybe a stranger saw the paper tags, figured it was financed, and checked for the GPS to disarm it.
I don't know that I've ever seen a case on here of a car jacking or kidnapping that wasn't quick. The perp would grab the intended person, and quickly gain control over them, then take them, or rape and kill them at that location. Since DV hasn't been found, I think it's ok to say she must have been removed from that area, if something was done to her.
Though come to think of it, Alexis Murphy willingly followed her abductor/murderer from a gas station to his property, where she murdered and never found.
So it IS possible that DV was in control of her vehicle, and followed car3 to wherever it went. Or she was in control and left the gas station and car3 followed her. So the actual crime scene might be someone's house, or on the side of the road somewhere.
Of course also possible there was more than one person in car3 or in the car with DV, and one of them took control of her car and drove off in it. Otherwise I can't see how both vehicles left and DV disappeared.
Which circles my brain back around to wondering if she knew car3 occupant/s and willingly drove off to meet at another location. Right now, I "THINK" that's my theory.