http://starcasm.net/wp-content/uploads/2014/12/Charred-remains-of-Jessica-Chambers-car.jpg
I showed my firefighter friend the picture of the interior of Jessica's car and asked him if it's possible that the fire could have caused the back of the seat to be reclined that way and he said he seriously doubted it. It would appear then that it was reclined that way deliberately. It is reclined way too far down for anyone to be able to drive that way and especially someone of Jessica's size.
I am still of the belief that something sexual took place in that car, whether it was forced or consensual. The position of the seat just makes me believe that even more. I am leaning more towards it being non-consensual and the fire was set to try and destroy evidence of any fingerprints or DNA. I also firmly believe it was someone she knew. If it had been a random attack, there would be no need for whoever is responsible to dispose of her phone as it would provide no direct link to that person/s.
There are only a few scenarios I can think of that can explain the seat backs position if it isn't sex related...
1. Someone reclining the seat so you aren't visible to the public to perhaps do some kind of drugs, like smoking some pot.
2. Her car is on fire and she is wearing her seatbelt and can't get it off. Recline the seat to try and slide out from underneath the belt.
Imagine you are driving down this road and come across a car on fire and you see someone in the car. What are you going to do? More than likely you are going to stop and try to help that person escape. I know I would. Now if you are driving down the road and see the car on fire, but don't see anyone in it, what will you do? Some people grab their phone and call the fire in, but continue driving. Some may also pull over, but at a safe distance to call it in.
3. Jessica is unconscious prior to the fire being started. The person responsible reclines the seat to keep her out of view from any potential motorists driving past, then starts the fire and flees.
Out of those three scenarios I think #3 is more plausible, but don't believe any of those three happened. There are a couple of things that I am wondering. We know that the fire was called in by a motorist and when firefighters arrived, her car was engulfed. What we don't know is did the motorist actually drive past her car or did they see it from a distance? When it was called in, was the car engulfed or just a small fire? If they drove past her car, did they stop even if only for a few seconds? Did they notice if there was anyone in the car?