I don’t think I’m underestimating how easily a young attractive female might find somebody with a car willing to take her far, far away.
To where? Disappearing without a trace would take an insane amount of planning. She needs money, food, and a place to stay. And she'd have needed to set it up without using any social media, phone, or email because all of those have been checked at this point. It takes a heck of a lot more than flashing a smile at someone with a car so they drive you somewhere.
This is not a mob boss or a hedge fund manager with a private plane we are talking about. This is a 20 year old girl from a small town in Iowa who has never been out of the country. She may be a very smart girl, but disappearing without a trace takes an understanding of banking records, technology, the underworld, and law enforcement that she could not possibly be capable of.