I'm now about 99.9% sure she's pregnant, since we can see the babies making her belly wiggle around. It's too cute. Of course, she's still being nuts and acrobatic and jumped from the third story to the bottom floor, so I hope she doesn't hurt herself or her babies.
I got the bottom wire covered with some thick fabric (I cut the fabric to fit the cage, with some strips that I've used to tie it in at the corners of the cage so that they can't easily move it). Now I just need a bigger house/nest box. I can't find anything at a pet shop in a reasonable price range, so I'm going to turn the cardboard carry box we got them in into a house by cutting a door into it. If they eat it, oh well. It was free.
I'll continue to keep everyone updated on her progress. Seems like it shouldn't be too long before we have a degu family.