Question about the ending....SPOILER

I see it's been years since anyone posted in here, so I know the likelihood of anyone answering this is low....

I'm confused about whether or not she was a ghost? Or her "journey" was an afterlife experience? The ending where she sees the town in the valley suggests the Native boy was a ghost since he disappeared suddenly...but I'm wondering if she was actually the ghost?

My reasons are that she wasn't dressed properly to spend days in the snow without acting like she was suffering from it. Why didn't whoever killed her husband also kill her? She wasn't hidden all that well in the wagon, she could have been easily found. That would suggest to me that she was killed. It also seemed like they had almost reached the Willamette Valley when the husband was killed since she didn't have far to travel before she found a town and her Bible had months worth of days marked off as tracking. I found it inconceivable that if there were Natives or road bandits in the area to have killed her husband that she was able to travel alone for days and not be found by one of them.