Glad to hear she went back to the eggs once put back in her original box. Some birds will accept the move and others won't. Silly birds.
As for seeing life in your eggs....
DH gave me one of those coop kits for Christmas. I have a large coop that my bantams occupy and two smaller coops that standard sized buff O's and Welsummers live in and then a bachelor pen. The kit is put together and sitting in our shop waiting for spring so I can move it outside. It will be my broody and grow out pen. But in case a hen doesn't want to be moved, I have a back up plan in the form of a nest box that sits on the floor of the coop under the regular nesting boxes. The hens lay in it and are comfortable with it so if one doesn't want to be moved, I have three screened panels that I can put up around the lowest nesting box and use it as a broody pen.
I've learned the hard way that when it comes to chickens, I always need a back up plan.
Have you marked your eggs? Other hens may be determined to donate to your broody's project so I would make it a point to check under her for donated eggs, just in case your BO hen decides to add to the two your little girl is sitting on.