If I understand you correctly, you've got a Leghorn sitting on a nest of her eggs, then you have 2 other nests that have eggs left in them (hoping for a broody I presume), but there is always a different hen sitting on them?
Hens will instinctively want to lay where others have laid before, which comes from natural instinct to add to the flock's clutch. Once the clutch is big enough, the broody type will be triggered to begin to brood. (There is a pressure point on the breast that releases hormones to brood once enough pressure is applied...ie a certain size of clutch).
That's why leaving fake eggs in the nest can help hens lay where they are supposed to, and letting a clutch develop can entice broody types to sit.
If you don't want hens trying to lay on these 2 nests, take the eggs up.
If you are trying to entice a hen from your flock to brood, you may just have to wait and see if your flock is composed of breeds such as the Leghorn, If that is a commercial hatchery stock, you may have a very long wait. It is very, very, unusual for a hatchery quality Leghorn (or other commercial layer types such as Production Reds) to ever want to brood. They will very occasionally do it, but that is rare as you are fighting against years of genetic selection to obtain high egg production (ie not brooding).
If that is not what you are asking, please post again.
have an over abundance (9) of broodies only 3 spots to sit and brood. Working on another coop currently so planning accordingly as didn't think we'd get but one or 2. guess the leghorn is mean enough they don't try to take over her nest, I have 6 of the broodies switching out themselves who is sitting on which of the other 2 nests