Ok, I'm back. L4H is right with the box. You can put the towels in. You could try straw if you have some available. Something that is close to what she would have been using outdoors may do the trick to settle her. Even some shredded newspaper if she wants to arrange it.
If you can get a crate then put a box in the back of it and let her do her thing. See what happens. Hopefully she will settle.
It is completely normal for her to be acting the way she is. Indoors is a foreign concept to her. If she can smell Aztec it will be adding to her angst as well.
How long ago did it dawn on you she was pregnant? (using your words) Because most vets will now abort almost right up to the time of delivery. Within a week or two. Could you ask MF and see what they recommend?
I believe you are doing the very best you can do for her. As I said, hang in there. Feral kitties are an all together different ball game than tame ones. You had her trust once. You can do it again with patience.
