I don't know but one theory I lean too is that whoever killed her that day was trying to meat with her but not murderer her. Perhaps he happen to be driving by and spotted her, pulled over...maybe they talked perhaps they pulled over there...it was hot she could have gotten in the car because it had AC...perhaps they talked there perhaps they drove somewhere else. When I use to come home from grad school some of my guy friends would come pick me up and we'd go find one of these spots to sit and talk and smoke weed. Not suggesting she was smoking...just saying I don't find it that weird to hang out in a car on the side of the road to have a conversation with someone, especially when you live at home with your parents....anyway....say things escalated and he snapped...she's dead and he now has to figure out how to cover his tracks...so he stages it to look like a random crime of opportunity...he tries to make it look like the work of a deranged serial killer but with only a Hollywood idea of crimes.
This theory could explain why he wouldn't have been concerned about his car being seen ...because he didn't realize he was going to commit murder...
He returns her to that spot because it gives him sort of a place to hide her and lines of sight to know he could get her out of the car and down the path without being spotted.
All of that seems more likely to you than just a poor split-second decision by someone who was in a state of sheer terror?
I'm not saying that what you suggest is impossible, but it doesn't seem more probable.
I know exactly what you mean about her possibly hopping in the car with someone, but here's why I don't think that happened in this case:
If she did get in the car with someone it wasn't a plan to meet up because her electronic footprint would have revealed this by now to LE. ( Facebook chat, texts and cell phone).
So that leaves only the possibility of somebody driving by and happening upon her (maybe this person was a really good guesser, and he times it right somehow, which is unlikely and difficult in and of itself).
She has just left her moms only five minutes previous. (she is possibly seen walking and talking on the phone at this point by the witness) law-enforcement can easily figure out who was on the other end of that call. most likely that call ended normally. She continued walking.
Joe Schmoe from Leominster pulls up beside her. She hasn't seen the old Joe for a couple years maybe. Hey let's catch up, hop in.
At this point she either gets in or refuses.
Let's take the gets in route.
She could just stand there beside his vehicle and speak with him but let's say She gets in because he's in the AC
but he is in the road at this point with his foot on the brake.
He pulls over to the shoulder near the path. Likely more than one car drives by them while they are sitting there on the side of the road. somehow things go wrong and he kills her right along the road. He takes her out of the car and drags her back in the woods. His car has been there the whole time they were chatting, and now the additional time that he is in the woods with her. He knows people saw it there. If he kills her in the car, I think he drives elsewhere- NOT THAT FAR, because he has a body in his car, but he drives elsewhere in Princeton. To a more secluded place. And dumps her there.
If they drive off together, with her still alive, he does not try to throw the case by going back to the abduction/meeting scene. That is riskier than any other alternative in terms of him possibly being identified.
So I just can't see it