Hi,
Laying once a year is fine. I would not encourage her to nest. She’s too old, and it’s never a good idea to add nests when you have more than one pair in a cage. Even in a large aviary, trying to breed with multiple pairs or birds is not recommended. Breeding birds get very territorial, and even in a large aviary, they really do not have the space to establish territories. This means you end up with birds raiding each other’s nests, destroying eggs or killing chicks. Adult birds will kill each other when one ventures too close to where a pair is nesting. Since she hasn’t truly bonded with a male, probably the eggs would not be fertile. And with cockatiels, the male and female take turns sitting on the eggs and caring for the chicks. So the best thing to do is discard the eggs and discourage her from nesting. You can block the areas she likes with toys or something else.
Thank you for asking Lafeber,
Brenda