Just brainstorming another scenario ...
Was SW trying to physically escape someone(s) after 1pm 9/19? A high-speed chase might explain the insanely short timeline from the 1pm FaceTime call to 2pm burning car. In my view, she would have been going at a very high rate of speed to make such a long, clean, straight swath through that tall cornfield, what with all the bumpy dirt rows and 'blind' driving. (Whoever) drove through that field was flying. It appears the only thing that stopped her was the ditch. Then, did her pursuer catch up to her? OR did she exit the car and flee on foot into the woods? Not knowing the vast rural area, desperate to elude her pursuer, she very likely wouldn't have noticed Keith Lane's DEAD END sign, so when the road ran out she just kept going straight through the cornfield. Overheated from the high-speed chase, could the engine have caught fire and incinerated the car after catching dried corn stalks as tinder? (We've all read news stories of vehicles totally engulfed in flames due to accident / mechanical reasons, i.e. non-arson.)
Other observations -
I find it interesting that her body was found along WITH her sunglasses and hat. She was apparently fully clothed(?). Of course, killers can manipulate crime scenes. Either she died at the FD on her own or the killer went out of their way to leave those items with her (why?). If someone killed her, why in the world leave her at a fire station?!
If the perp(s) didn't want her car, didn't steal from her and didn't sexually assault her, that pretty much leaves accident or suicide.
When did SW arrive in MB and how long had she been there before she disappeared? 553 miles / 8-9 hours is a long, tiring drive for anyone, even a 21 year old. IF she had just arrived in MB on 9/19, why was she trying to rent a scooter? Makes no sense. My guess is she arrived in MB at least the day before and more likely, days before. Yet she never saw her father, who reportedly, was the reason for her trip. Sigh. This case is so sad and frustrating.