You wrote "won't let us" in to see if she's on any eggs. Describe how she won't let you.We have a 6 month old hen- part EE, who won't get out of a box in the coop. No idea if she has an egg under her- she won't let us in to see. Is this a typical behavior ypu'd see in a broody or sick hen?
Take her off the nest and see what she does. If she's broody she'll likely come off the nest in a trance. When she snaps out of it she'll get some food, keep up with a cluck cluck clucking, walk around like a turkey then head back to settle on the nest.
Sounds like a broody.