It's a very sad story and somewhat hard to understand, but she actually survived 26 days after getting lost according to her journal entries. So she had some survival skills, but somehow just couldn't find a way to hike out.
I think this situation will always be somewhat of a mystery:
"The camp was less than two miles from the Appalachian trail. Adam wrote that walking south from the campsite, the dense forest became open woods with good visibility after 60-70 yards, and after another 25 minutes he found ¡°a clear logging road¡± that led to lodging. In total the walk took about 30 minutes."
ravi_jmt2013