She's just trying to keep them in the nest while she waits for the rest of the eggs to hatch. She may not be able to keep them in that long, that's along stretch between hatches.
You may want to take the chicks and brood them yourself, with a light in a box, until the others hatch. Just make sure they have room to move away from the light if it's too warm, and give them chick starter, and water in one of those screw on chick watering founts you screw onto a quart jar. I put pebbles or marbles in the water tray so they can drink ok, but not get wedged into the tray and drown. (It can happen. I've seen it.)
Otherwise, she may leave those last eggs, in order to stay with the hatched chicks. In nature, live chicks take precedence over potential chicks.
As soon as the last chicks are actively running around, you can put the first ones back in, usually with no trouble. you can either (A) Slip them under her at night, from behind her, where she can't peck you or the chicks, or (B) Pick up all the chicks, mix the ones you're adding back in with them, and turn them all loose at once. They should all run back to her, and she'll just growl and cluck and gather them all to her.
