Many younger people have no idea what it was like in the 70's and 80's when personal communication devices and trackers were only known in Star Trek.
They have no idea how to even live if they cannot monitor and be monitored, si your girl is in reasonable company by today's standards.
I'm no doctor, but maybe she doesnt suffer anxiety beyond the modern, normal "yikes, I'm disconnected from everything." I dont know the answer to that.
I would sit calmly with her and address each of her "What If's" in turn. Have her give you a "what if" and counter it with calm, factual, knowledgeable advice. And if you yourself dont know the answer, look it up together. "What if a bear...blah blah blah" might be countered with the fact "there are no bears here, but IF we were near bears, this is how we behave and this is what we do." And so on.
She might still be nervous, of course. But as other have said, take it slow. Go to a local place,. Get comfy, and expand your circle. And...as you do that, give her very specific, helpful tasks to do. At home, teach her how to pitch the tent dir example, and have her do that when you get to camp.
Teach her some tracks of the animals she fears. Have her do a quick scan around camp upon arrival.
Maybe she is good at starting the fire. Have her do that while you pitch the tent. Whatever it is. Give her the knowhow to recognize signs of those things she is afraid of and set her looking for those signs. If she doesnt find them, then get busy on task. That should give her confidence that the area is safe, and the confidence to know how to perform the task at hand.
After that, do another check of the area, have dinner, a drink, and turn in.
Keep doing that and expand your area and the tasks.