Hi Lyubov,
It’s actually better that she isn’t interested in the egg. This can mean she won’t keep laying eggs. She does not need a nest since she is a single bird. Nests are only for eggs – birds do no sleep in nests in the wild. So a single bird never needs a nest, and a pair only needs a nest during breeding season. As long as she doesn’t care about the egg, you can discard it. She may lay more, but as long as she only lays 3-4 eggs, this is normal. If she won’t stop laying eggs, and won’t sit on them either, you might have to take her to a Vet for a hormone shot. You can try limiting her light to 8-10 hours by covering her cage early each evening. Have her cage in a busy place in the house, and move it to a different place once a week. This can generally get a bird to stop egg laying.
Thank you for asking Lafeber,
Brenda