My cat didn't want to have anything to do with her nesting box until after she had her kittens. We had the box in my sister's master bath because it was the only out of the way place. She had paced around all day so we put her in the bathroom, and I decided I couldn't go to sleep and hope that she would wake me when she started labor with her crying, so I put a blanket in the bathroom intending to sleep on the floor in there with her, and as soon as I laid down she laid down next to me, and began pushing out kitten number one. The best I could do was but a towel on the floor and let her have them there. In the morning I moved them into the box and that's where they stayed. It's quite possible she wants you there for the delivery, maybe you can get a sitter. I know Phoebe wouldn't have hers without me there, everytime I moved even a little, she got up and started acting nervous. I've never been so still for so long.
Good luck with your kitty.