You can candle them to see if they are developing. You don't need a fancy egg candler to do that, just cut an oval hole in a piece of cardboard, about half the size of the eggs. Put it over a light source and place the egg on the hole and look for a shadow of the chick. Toward the end hardly any light will come through at all. I ususally do this in a dark room. If nothing hatches, you can still set her in an isolated spot with a new bunch of eggs. I used to set two hens at once, then give all the chicks to one hen and re-start the other hen with more eggs. Don't worry about bothering her, she will be fine.
