Did the egg rock around when she float tested it? A live chick doesn't like being floated and the egg should jerk. Can you hear it tapping inside the shell, trying to pip? They will chirp to connect with other chicks and the hen, then get down to the business of breaking out.
It's important not to interfere as trying to 'help' too early is dangerous for the chick. They need to finish absorbing their yolk and the blood vessels need to close off before they actually hatch fully. There's a lot going on between pipping and hatch. I'd only help if the chick has pipped externally and hasn't progressed for at least 24 hours, but that is difficult to judge under a hen. Try not to take a pipped egg out from under the mother hen as her body is keeping the humidity high enough for it to hatch safely and prevent the membrane from drying out.
I know it's difficult though - it's so hard waiting to see those gorgeous little chicks! If it doesn't hatch you've got to trust that it wasn't meant to be and be glad you have one little cutie.
