Average walking speed is 3 miles per hour, a fit person could do it in 4 hours. But then allocate time for a meal and snacks, viewpoints, etc.I wonder what the terrain is like? Hiking 11 miles in a day is quite a pace. ....
Unlikely that she veered off this well-marked trail IMO.
JMO
There are many reasons to go off a trail: toilet break, or to get to a view, or to take a photo.
In the case of a woman who disappeared from the Appalachian Trail, she went off trail to take a pee break and got completely lost.
I don't know what the features are of this part of trail, but I'd look for anywhere someone might go off trail and get too close to an edge, as that's what I think of when.they say mountain.
JMO