This is so very sad. I wasn't aware of this case, but it made me emotional thinking of my own mum around the same age.
Very unusual victim, hence why police were immediately concerned. I noticed (I think) that there is no mention of a husband being worried - just daughter. I may have missed this, but is Sherry single? Sherry is an older woman, seemingly middle class (I could be wrong, but her facebook pictures, car, etc. give that feel). I can't imagine there would be a lot of drama or enemies at that point in your life, which leads me to believe it's someone she already knows. I'm guessing it's not a current new love interest, as I feel that would have been more chaotic. This seems like they had the a goal and they had planned it out well. This seems too well thought-out to be a crime of opportunity (need to know backroads, know the route to get away, have something to start a fire). Based on a guess alone, I would think that she knew the suspect, the suspect got in her car with her, and then forced her to the remote location. The personal items thrown out of the car seems like an attempt to make it seem like a robbery of some sort - staged. It seems like this person didn't want to get messy about it and just wanted it done, which makes me think that the way they killed her probably wasn't very physical. Taken together (and knowing very little about the case), I'm getting ex-husband vibes from it.
Again, all hunches. I want to remain respectful of this case.