Hi Valentina,
I’m so sorry this happened! When a bird gets loose, they often fly wildly until they run into or land on something. So if she went too far, she may be lost. If she is really tame, she may go to someone, so be sure to put out flyers. If she is close, she would likely respond to the male calling for her. But he probably isn’t calling since he is on the eggs. He will not be able to do this alone. Most likely he will leave the eggs tonight and that will be the end of them unfortunately. I’m surprised they have tolerated an extra female in the cage. It is unlikely she will help since she isn’t the mate and he likely won’t allow her near the nest box. She is smart to have avoided them and this is most likely why she is still alive. You can’t have an extra bird in a breeding pair’s cage. They will attack and kill an extra bird because it is a rival. And most of the time, the extra bird will be jealous of the pair and will try to raid the nest to destroy the eggs or kill the chicks. I can’t stress enough how lucky this extra female is to have not been attacked or killed by the pair. It’s sad about the eggs, but there isn’t anything you can do. They don’t artificially incubate well, and when you try to hand feed cockatiel chicks from day one, they almost always die. If the female returns, you need to take the extra bird out. It is never a good idea to keep an odd number of birds in a cage even if they aren’t breeding. Even if they are all the same sex, they will usually pair off and leave one bird on its own. That bird is often bullied and attacked.
Take care,
Brenda