Welcome to BYC!
She sounds broody to me....on the nest most the day
and all night for 2-3 days running is when I call 'broody'. There are other signs that once you are familiar with them are obvious. One of the most telling is the low repetitive cluck-cluck-cluck-cluck-cluck, the 'broody cluck' and why broody hens are also called 'clucky'. Laying on nest all spread out 'flat as a pancake' and will drop to the ground in same posture if removed from nest. The feather plucking of breast and belly is telling too.
You'll need to confine her for more than a day, egg binding is not likely, it can take a week or so to re-habituate them to laying in the coop nests. Hopefully your coop and run is large enough to keep the whole flock confined to get the job done.
Free range birds sometimes need to be 'trained'(or re-trained) to lay in the coop nests, especially new layers. Leaving them locked in the coop for a week or so can help 'home' them to lay in the coop nests. Fake eggs/golf balls in the nests can help 'show' them were to lay. They can be confined to coop and maybe run 24/7 for a few days to a week, provided you have adequate space and ventilation, or confine them at least until mid to late afternoon. You help them create a new habit and they will usually stick with it. ..at least for a good while, then repeat as necessary.
Some folks warn against letting a pullet(female younger than one year)brood, they may not be good at 'mothering', might not stick with it for the 21 days, etc......but it can work.
You'll need to decide if you
want her to hatch out some chicks, and how you will 'manage' it.
Do you have, or can you get, some fertile eggs?
Do you have the space needed? Both for more chickens and she may need to be separated by wire from the rest of the flock.
Do you have a plan on what to do with the inevitable males? Rehome, butcher, keep in separate 'bachelor pad'?
If you decide to let her hatch out some fertile eggs, this is a great thread for reference and to ask questions.
It's a long one but just start reading the first few pages, then browse thru some more at random.
http://www.backyardchickens.com/t/496101/broody-hen-thread
If you don't want her to hatch out chicks, best to break her broodiness promptly.
My experience went like this: After her setting for 3 days and nights in the nest, I put her in a wire dog crate with smaller wire on the bottom but no bedding, set up on a couple of 4x4's right in the coop with feed and water.
I used to let them out a couple times a day, but now just once a day in the evening(you don't have to) and she would go out into the run, drop a huge turd, race around running, take a vigorous dust bath then head back to the nest... at which point I put her back in the crate. Each time her outings would lengthen a bit, eating, drinking and scratching more and on the 3rd afternoon she stayed out of the nest and went to roost that evening...event over, back to normal tho she didn't lay for another week or two. Or take her out of crate daily very near roosting time(30-60 mins) if she goes to roost great, if she goes to nest put her back in crate.