My take on it,
Her car was planted where it was found to mislead the cops.
Due to that, expect more than one person to be involved in this.
I think the intent was to bury the car in the bushes so deep that it wouldn't be found for quite some time, but the 4 x 4 capabilities of a compact car aren't all that good, so it was stuck and abandoned where found.
It's locals, someone who was observing her while she was shopping in town. Locals would also know of good out-of-the-way spots to get rid of things.
Her cell phone was taken and discarded prior to the car being parked. If her car was commandeered, it most likely happened in a public place. The phone would have been immediately discarded to eliminate tracking.
Think Holly Bobo, this is going to sort of mirror that, only with a few tweaks in the details.
They need to flood that entire area with missing persons flyers and media reports, help remind people what they may have seen that day without realizing it. Establish if it was her or not at the shopping center. Try to track both her movements and her car through video surveillance cameras set up in that area, working backwards from where the car was found to the shopping center.