I do not want to read her mind from a distance and ascribe motives. That would be a bit crazy. I will leave it to others to figure out if she was suicidal, homicidal or insane.
Her being only 20 miles from the highway might not be something she knew either. After all, she drove over 30 miles down the trail before she got stuck.

Parts of the story indicate some self reliance like being able to change a tire, trying to get to a high point and try calling on the cell phone, etc.
Maybe she simply got lost and didn't know how to locate herself.
Lots of us take wrong turns and she seems to have turned the wrong direction at least twice. I have even seen people lost with compasses, GPS and maps who simply would not believe where they were or which way north was until you walked them out the trail to their car.
Oh well...

Maybe the only lessons we can glean out of this is how bad things can fall apart when they start to fall apart and how it is important to be ready for it when they do.