Her face is red which is a good indication she will begin laying soon. However, her comb is still small. Is she squatting? How about singing or checking out the nests? These are also great indicators that the eggs are close to coming. In the meantime, I would recommend putting some fake eggs in the nests so she knows where to lay. Also, watch for her comb to grow in size.
Check the space between the pointy pelvic bones. That has to expand before an egg can pass. If it is over 2 finger width and the vent is moist, laying is imminent.
IMHO, not all hens will squat and the egg song usually doesn't come till laying commences. Squatting is the desire to breed, not that they're about to ovulate. Hens with roosters will almost never squat for a human.