I doubt very much if you can entice her to go back to finish the job. She's doing what God designed her to do. In a normal situation, the hen would visit the nest every day until she had accumulated a clutch of eggs. Then, she'd hike up her skirt, and hunker down for the prescribed 21 days. They'd all hatch at the same time. She'd sit tight until they were all done hatching, then take them out to learn how to be chickens. By adding eggs to the nest after she'd started incubating, an un-natural situation was set up. So, she's taking care of the ones who have hatched. To stay on the nest for late comers would put those already hatched in jeopardy. That's why we wait until a hen is proven to be broody, and give her a whole clutch of eggs at the same time, and remove any late entries. So, your best bet would be to bring all the rest of the eggs inside, and rig up a lamp, over a nice warm towel, perhaps with a dish of water for humidity. You want to aim for 99 - 100* at the height of the eggs. Good luck, keep us posted.
