As the girl's chains fell off, she walked towards the light and I bet it hurt her eyes because al of her life was shadows, no light.
Owww my eyes!
The girl walked behind the kids sitting and got a glance of everything, she even walked out of the cave
Maybe I should get out of here.
Then, she walked back in the cave, sat in her normal seat while the shadows were being projected and since she came back from seeing the sunlight, her eyes were completely useless and as a "poof" or tree was being projected she says it's a tree and the others were like no, it's a poof.
To add, the other kids in the cave haven't experienced the real world, all they know of is shadows so what is actually called a tree, is a poof to them.