If she feels safe in the apartment, and has access to it when she's ready to deliver, that's probably where she will go. In fact, if your boss does not have any objection, and you can leave enough food and water and a litter box for her for the three days you are not there, it might be best to go ahead and bring her in and let her start looking for a nesting place. If that's not possible, though, you might want to help her find a dry, safe, quiet place free from drafts and moisture, and help her make a nest by finding her a largish cardboard box and putting newspapers or old but clean towels or blankets in it. She might not use it, but I've had a foster and a stray that were pregnant when they came into my home, and both of them used the nest I made for them. I wathced them so I could see where they were poking around, and put their boxes where they were spending most of their time. They both took to them, in fact they seemed to appreciate my help. The day she's ready to have them, if it occurs when you are at work, you might notice that she seems listless and uncomfortable, you may see that she's not interested in food or even water. She may even get sick to her stomach. This will mean she's going to deliver within a few hours, so if you notice this, and you have tried to make a nest for her, you might encourage her to go ahead and get in it. But she still may do what she wants, when she wants, and where she wants. But she seems to trust you, so it might work, and then you can help assure the kittens (and her) will be out of danger while they are still so helpless, plus if you know where her nest is you will be more able to assist her those first few days after their birth by bringing her food and water (she won't leave the nest, even if it means she goes hungry, for the first few days). Good luck with her, and keep us posted!