Split the couple up for a short time, reduce protein in their diet and restrict daylight hours to 8 hours only.
Splitting the pair up will bring the hen out of breeding condition. It's best, if possible, to keep her in a different room, but if not, just in her own cage without any males will help.
If your hen lays an egg there is no 'killing a baby' when it is first laid.
It's the same as any shop egg at that stage so it's the same as throwing away any egg.
The hen needs to incubate the egg for quite a while before there is an actual life.
I successful bred a pair this year and threw away several of the eggs to keep her clutch manageable for a first time mum. There's no need for sentimentality with an egg. It's very different to an egg that has been incubated for days.
Preventing them laying eggs is your best option.
Going into breeding because you don't want to throw away an egg would be dangerous for your birds.