Say on the second day that she has picture perfect memory. Say that as she's walking down, she's remembering every last detail in perfect sync with the clock from her hike up the day before.
Physically her body is going down. Mentally her body is going up. They're both on the trail at the same time, one physically going down, the other mentally going up. At some point on the trail, her physical body is going to run into her mental body. It has to happen. It can't not happen. And when it does, she will have reached the same spot at the same time.