Congrats on the babies! They are adorable fuzz balls!
I had a silkie hen who was sitting on some eggs and I allowed her to stay on however long she wanted, which was maybe 24 hours or less? I took the one egg that didn't hatch and put it in an incubator, but it never did hatch. So she probably knew that it was a dud.
So from my personal experience, I would let her sit on the eggs however long she wants. She will probably leave the eggs for the good of her chicks eventually, but the chicks don't need to eat for a couple days, so they won't be put in danger if she sits on the eggs for a bit longer. If she's still on the eggs and it's been 3 days, maybe it is time to take away the eggs. I didn't have this problem though.
Take it into consideration that this was a one time experience for me, so hopefully others can give their advice.