Things you can do to try to prevent egg laying can include:

Don’t provide a nest box (although she is likely just laying them on the floor).  Sometimes just seeing a nesting spot can trigger an egg laying episode, such as an empty corner of a bookshelf, the space under a piece of furniture or a partially opened drawer or closet.

Don’t kiss your bird on the beak as this can simulate the allopreening (feeding each other) that is often seen in bonded pairs of parrots.  That encourages her to see you as her “mate”.  Keep your kisses to the top of her head.

Don’t pat your bird on her back, don’t touch her tail or vent area.  Those things can simulate the feel of the male on her back which is how cockatiels mate.  He gets on her back and she moves her tail to the side and he swishes his tail back and forth like a windshield wiper rubbing vents together.  So avoid those areas and keep scritching to the head area only.

If she can position herself under a toy so that the toy is resting on her back, move the toy so that she cannot do this.  The weight of the toy on her back is enough to send her into an egg laying episode because it can also simulate the feel of a male on her back.

Cockatiels don’t have a “breeding season” like many parrots do, so this may not be all that effective on a cockatiel, but you can try to reduce the amount of daylight to 10 hours a day and keep her covered and in a darkened quiet room for 14 hours each night.  This is hard for a person who works 8 hours a day outside the home, not including commute time too, because you might end up covering your bird at 6pm and uncovering the bird at 8am and that doesn’t always work for someone who is working full time outside the home.

You might want to cut back on the availability of soft foods (temporarily at least) because often an abundance of soft foods can trigger an egg laying episode.  When a bird has an abundant food supply and it is the type of food that is easy for them to bring up (regurgitate) to feed chicks, that can help trigger egg laying also.  Soft foods are more comfortable to bring up as opposed to harder foods like pellets or seeds, but soft foods (leafy greens, whole grain bread, cooked whole wheat pasta, cooked brown rice, veggies like shredded raw carrots or shredded raw broccoli, warm green peas, etc…) come up easy and are comfortable when doing so.

If your bird is receiving weekly baths, you might try cutting back on that for a little while.  When a hen lays eggs, she likes to sit in water now and then to help provide a little extra humidity when needed because a little humidity can prevent the developing embryo from sticking to the inside of the egg shell.  The hen seems to instinctively know when extra humidity is needed.

If you can rearrange her environment some that might remove the “comfort” level she feels with her cage, its location and the familiarity of the perches and toys, etc…  When someone buys a “proven breeding pair” of parrots, the move to the new home and new surroundings, perhaps a new aviary cage and nest box, etc…it often takes the pair a couple months or more to settle in to begin breeding again. 

Don't allow your hen free flight around the house.  This enables her to find many suitable nesting sites and can also help to facilitate an egg laying episode.