Sorry to hear she's not doing well. It stinks. :hugs
Technically, yes, you can leave a chick in the incubator that long, they have egg yolk that they can live on.
But if they hatch already lethargic and with splay legs, can't get up and start moving around, then you either leave them...
She needs to be out of the incubator.
You'll just have to monitor her closely to make sure she's not overheating. You're going to be giving her drops of water every so often as well.
I'd give her drops of the sugar water or if you have it, Poultry Nutri-Drench (2-3 drops twice a day and plain water too).
It would be a good idea to get some B-Complex and give 1/4 tablet daily, this can be dissolved in a small amount of water and drops given throughout the day.
A tiny...