Not to sound rude, but if you don't even realize that 12 week old eggs are not fertile, nor do you know how to candle eggs to see if they are fertile, then you shouldn't not be breeding your birds at all, as you will not be prepared in any way to take-over hand-feeding babies if the parents stop feeding them, start hurting them, or kick them out of the nest box. I'm guessing you didn't prepare BEFORE allowing your birds to mate by buying any of the things/equipment you'll need if this happens, like a Brooder, hand-feeding formula, hand-feeding syringes, a candy/cooking thermometer, and the medicines/supplements you'll need to add to the formula if problems arise. NONE of what I just mentioned are optional, as without any of them the babies will die.
And you also will not be able to help your female if and when she becomes egg-bound from laying so many eggs over such a long period of time. That's a lot of eggs that she's laid and it's been too long a period of time, I hope she is on a high-protein, fortified pellet diet with supplemented fresh veggies and fruits every single day, along with added calcium every single day from a mineral block and a cuttlebone, along with an Avian multivitamin and probiotic supplements. Hens become egg-bound typically from laying when they are too young, laying too many eggs in one clutch, laying too many eggs in too short a period of time, and most of all from not getting enough calcium in their diets. WHEN A HEN BECOMES EGG-BOUND SHE WILL DIE 100% OF THE TIME WITHOUT IMMEDIATE MEDICAL INTERVENTION, AND IT IS A HORRIBLY PAINFUL WAY FOR THEM TO DIE...Do you know how to tell whether or not a hen is egg-bound? Do you have a Certified Avian Vet and an Animal Hospital with at least an Exotics Vet that is open 24/7 within driving distance in case this happens?
There's usually a very good reason that eggs laid by a mating female parrot are not fertile, usually it's due to inadequate circumstances, living conditions, ages, and diet. So please pull the nest box out until you buy everything you need and educate yourself on everything you need to BEFORE you end up with babies that you cannot care for or a dead hen.
By the way, 18-21 days is about the egg incubation period from the day they are laid until they will hatch, so you have eggs that are not fertile after 3-4 weeks, no need to wait for 12 weeks. You may also want to invest in some fake plastic eggs so you can pull the real ones, freeze them overnight, and then pitch them. Then leave the fake eggs in until your hen stops laying on them and stops showing interest in them. Then you can remove them. This will stop her from laying any more eggs as long as you remove the nest box and all nesting material/bedding from the cage as well. She needs a long break before laying anymore eggs. I don't know how old she is, I hope she's well over a year old because any younger and it's totally unsafe to breed her, but either way she cannot keep laying eggs the way you are allowing her to do so without eventually becoming egg-bound, malnourished, or both.