Out of dozens of broodies I have had one mom "ween" as early as yours. She was a co parent of a second set and stayed a bit longer the second time, but no where near as attentive as the other mom.
As far as what the chicks did? They took advantage of others sitting on eggs (Silkies) and found whatever warm spot was allowed. I noticed they grew slower than most chicks even though they had access to the same feed as others. She had one boy and one pullet that batch which I still have. The pullet seems to be kind of a loner.
Not sure if they would have faired quite so well in my large foul coop.