As far as Susan's concerned, she's never going back to Narnia. Aslan told them so, told her and Peter, but Peter always tries to tell her they'll go back someday - it's a lie, she knows, concocted to comfort Lucy and Edmund, and Peter himself. It's really rather childish.
As far as Susan's concerned, if she wants something she can't have, it might as well not exist at all.
Boys' skin is colder to the touch, here. They are far fewer, far less mature, far less good-looking.
The cloth here in England is too harsh on her skin, the wool leaves red marks on her skin where it itches.
The only comfort she can find is in her bedclothes at night, sheets smooth against naked skin; and if sometimes another body accompanies her - well, she is only making up for her losses.
Peter, as we know, tries to come to her rescue first. It is his job, as eldest sibling and as High King, to keep them all from breaking - Susan is as fragile as china.
Peter, don't be stupid, we aren't kings and queens anymore, and we never will be again. He said so. You're reaching out for the untouchable.
(She doesn't say Aslan anymore, doesn't say Narnia, and somehow she feels it is breaking Peter's heart.)
Then, it is Lucy.
Susan's always loved Lucy far more than her brothers. She was always the older sister, the one Lucy trusted for advice and to her secrets. But Susan's never hurt Lucy, would never dream of it.
But it's words that hurt the most. When Susan calls Narnia one of Lucy's old games, she might as well be calling her sister stupid, might as well go back to being twelve and naive and disbelieving.
(Susan doesn't hear her sister crying to Peter that night, doesn't hear her brother's quieted sobs joining Lucy's.)
Edmund never makes any attempts to appeal to her, only looks at her gravely; and when Susan almost remembers a time when it was Edmund who was the traitor, she almost thinks and now the tables have turned, and Edmund almost shivers. But you see, Susan doesn't remember much anymore, doesn't remember the sea on her skin or the wind through her hair or dancing late into the night in a blur of brightly-colored dresses, so as it is she only smiles at him smugly.
Edmund shivers anyway, because he sometimes thinks she looks like the White Witch.
(The Gentle Queen has never been more harsh.)
Moving on, Susan finds, is easier to do when there are others who must move on with her. That is to say, it is harder for her to leave Narnia behind her when she realizes she is alone with her efforts, when she realizes her siblings actually still hold some ounce of hope.
It is far more difficult to move on when she doesn't have anyone left. Her brothers and sister are dead, and not even the cold English boys stay with her these days.
She stares at the gray tombstones for hours before she realizes what is so strange about them:
They are the wrong names.
Her sister's does not say Queen Lucy the Valiant, her brothers' do not say High King Peter the Magnificent nor King Edmund the Just. The Pevensie children, to this world, were only beloved daughter, sister, brothers, sons, friends - nothing more.
Somehow, it is wrong.
She has an exam coming up. She is making notecards, or attempting to. She has dozens of Latin verbs written out, multitudes of nineteenth-century female novelists, but she sighs and looks out the window to the rainy gloom, sketching idly. This is her last notecard, and it is supposed to say something like Charlotte (or is it Emily?) Bronte, maybe it should say patior, pati, passus, but anyhow, it ends up reading Queen Susan the Gentle / September 30, 1928 - September 5, 1941.
(Susan died long ago, when she was told she could no longer return - but she doesn't think of this, only scoffs and opens her window, throws the notecard, the last remnants of her life in Narnia, out into the gusts to be driven underground with the force of rain, to be buried beside her siblings.)