An egg that's lagging 10 days behind will not make it, as the hen will leave the nest with the chicks that have already hatched, letting the remaining egg cool and die. I wouldn't pull the hatched chicks from her to encourage her to keep setting on the lagging eggs, as you'd be faced with reintroducing older chicks (10 to 12 days old) to a hen with a newly hatched chick, assuming it hatches. She may reject the older chicks at that point.
I'd be inclined to let nature take its course. Or, if you have an incubator, hatch out the lagging eggs and try to introduce those chicks to the hen at night, letting her keep any chicks she hatches in the meantime.