It's not dangerous if you have navigational skills. Most people, however, do not, or haven't developed theirs very effectively. I see it myself sometimes with other hikers at the front of a group—they take a wrong turn and suddenly have no idea where they are and start freaking out rather than just backtracking. Fortunately they're in a group, generally of people who can navigate and do know where they are, but when someone with poor navigational skills gets into that situation it usually leads to panic and bad decisions.
It's not at all extraordinary that a hiker of her age decided to go backpacking alone (which in this case she didn't—she was with someone else who left). It's a very common thing for people to solo hike and backpack. Carrying a small amount of gear is not a problem either—it's the norm. But navigational tools of some sort, even just a micro compass and a map, are generally considered an essential.
It's not at all extraordinary that a hiker of her age decided to go backpacking alone (which in this case she didn't—she was with someone else who left). It's a very common thing for people to solo hike and backpack. Carrying a small amount of gear is not a problem either—it's the norm. But navigational tools of some sort, even just a micro compass and a map, are generally considered an essential.