Hi Karen,
This is a very common mistake, and really it falls to the pet shop employees who don’t understand that birds only need a nest for breeding. As you have found out, yes, they will sleep in a nest if they have one. But then at some point you get eggs! Since you don’t want to deal with breeding, I would take the nest out. She may lay a few more eggs, but hopefully she will stop and not lay again, at least not right away. If she tries to use a food cup as a nest, replace it with smaller cups. Hopefully the cage has a metal floor grate – if so, the eggs may fall through, but if they don’t, they won’t hatch because she can’t keep them warm enough if they are on a metal grate. Without a nest, she may still lay eggs from time to time. It’s not an issue unless she does this over and over, such as every couple of weeks or every month. If you keep them in a busy place in the house, they are not as likely to breed. You can also limit their light to 8-10 hours by covering the cage early each evening. With a really stubborn egg layer, you can try moving the cage to another place in the room once a week.
Thank you for asking Lafeber,
Brenda