I think she must have gotten lost and disoriented while very close to the trail and then spent a lot of time walking in the wrong direction without paying enough attention to be able to retrace her route even back to that first place where she realized she was lost. At some point she realized that moving was getting her more lost and she stopped. But at that point she was too far away from the trail for the searchers to find her.

In fact, I wonder if at the end, once she'd set up a permanent camp, if she stayed put because she was flat out afraid she'd get lost again if she left the camp even to go a few yards. This might have been a legitimate fear, but there is a way to handle it -- you leave "blaze" marks on the trees as you pass them so you can retrace your route. But maybe she wasn't familiar with this technique.