Not discussed.... you've had her for 18 years. She does not have a mate. Even if she *IS* healthy enough for breeding, there's no guarantee that she would accept a male bird. You could easily end up with two birds that have no interest in each other, or perhaps one bird who is but the other isn't.
As mentioned, pets don't make good breeders (generally speaking). Birds raised to be pets are typically raised differently than birds raised to be breeders. Laying eggs and raising chicks can take a lot out of a hen... and she lacks experience raising chicks, so this means that if she were to accept a mate, you need to have the knowledge and experience to raise these chicks if she can't do it/you want to. This means it's best to have a mentor on hand who can help guide you through the process. Chicks that are parent raised are usually more timid and scared of humans than those who are hand raised by them.
On the flip side of things.... breeders don't make good pets. (generally speaking) *IF* she were successful at becoming a breeding hen, she may no longer be your pet. She may become aggressive and defensive and want nothing to do with you.
This isn't even going into the complications of breeding. Thing such as egg binding, egg peritonitis, dead in shell, chicks that fail to thrive, parents that underfeed/overfeed, trample chicks, etc. You need to be prepared for the worst outcomes so you can best handle any situation that arises.
My cockatiel, Casey, is 18 years old this year. (2 months exactly to this day!) She's also an occasional egg layer. Even when she was younger, she had *NO* interest in male cockatiels. I'm not interested in breeding, so this works for me. She accepts other birds, even cockatiels, as her flock mates, but she never got the "birds and the bees" talk. (even when it was happening right in front of her....) She was 100% raised by humans from the day she hatched (from my information). She understands that once she lays eggs she's supposed to sit on them, however for the life of her, she can't figure out how to get them all under her, then simply gives up and walks off to go do something else. She's a great bird, but she'd fail miserably as a mother!!!!