Oh, that stinks!!
The fake eggs are not to stimulate laying,
just show them a safe place to lay...or brood.
You may just have a perpetual broody.
Wonders what she'll do once her offspring start to lay.
Ah, well, I thought maybe she was laying out in a free range area.
You might just have to wait and see.
I was going to suggest an exam:
https://www.backyardchickens.com/articles/who-is-laying-and-who-is-not-butt-check.73309/
Then maybe:
Free range birds sometimes need to be 'trained'(or...
Could be the decreasing day length, could be the fact that she's still 'brooding' the 'chicks', could be a combo.
I'd have blocked them from sleeping in the nests long ago,
like by the time the chicks were about 6wks old.
Do you have other chickens?
Do they free range?