I want to believe Maura is alive. I want to believe she pulled it off, found somewhere safe, a better life. I will never believe she went up there without telling someone - and if that's true, there must be a good reason that person did not share that info. And I believe Maura was not traveling alone. However...
There is one clue that, on the surface, really suggests she never made it off the mountain - her cell phone.
It wasn't in the car. It went with her (unless we are to believe it was already thrown away). But it never rang again. Bill was trying to call her that night. And everyone was trying to call her the next day. But we know it didn't ring because of the phone records. No calls are getting through. Which means either it was turned off, or it was never again in range of a cell tower - that it never left the mountain, where there is no service.
In fact, for me, this would be case closed - evidence for sure that she ran into the woods (regardless of no footprints, the scent dog leading to the middle of the road) and died there, if not for one frustrating detail: we know Maura turned her phone off earlier that day and we don't know why. Bill was trying to reach her in UMass and after a while those calls don't connect. We know the phone was off as she drove toward the White Mountains. She turned it on once, to check voicemail, and then off again. It was likely off at the time of the accident.
The question is, why did Maura turn off her cell phone? Was it to conserve battery? Or was it so Bill couldn't follow her, couldn't call her?
Since it was off, did she just keep it in her purse, instead of, say, the cup holder or the passenger seat? So when she left, it came with her?
Again, we come to the fork in the road: either she ran away and the plan was already in motion, or she's dead in the woods. If she ran away, though, all the drama that happened in the days leading up to her disappearance (the email from Bill on the packed boxes, the party, the father visit, the money, the lying friends, searching for a condo with 2 bedrooms, etc.) make a certain sense. If she's dead in the woods, it's all just noise and she never told a soul. That's still really hard for me to buy.