I only day hiker occasionally. I take 2 flashlights, rain gear, survival knife and fire starter, GPS with extra batteries, paper topo map, regular compass, compass on my watch, twice the water I expect to use, food, cell phone, altimeter on watch, whistle, small first aid kit.
I am not an experienced hiker, but I think I have some common sense.
Yours is the first post on this thread to mention a whistle. Something absolutely basic for any survival kit. It would have saved this unfortunate woman.