The Last Tree In Narnia

Rhea is believed to be the last dryad in Narnia, after the rest of her tribe is killed. She is taken in by a a group of Narnians, who tell her that she will have an important role to play in the future.
She is the last living tree, as the rest have grown still over the years. If anything happens to her, the trees will never again be able to dance like they used to.

When Prince Caspian wanders into the woods and stumbles upon the Narnians, Rhea and Trumpkin the dwarf are captured by the soldiers looking for Caspian.
Being away from the forest makes Rhea grow weak, as she can't feel connected to nature, while locked in cell.
She longs to be freed, but she isn't sure whether anyone will get to her in time. And she knows that if she dies, so do all the forests throughout Narnia.