@courtenay   And probably the answer would be something like: "Child, that is her story, not yours, and her time in the Shadowlands has not yet ended" — but with a knowing smile that reassures us that there is hope for her yet, and that Aslan hasn't forgotten Susan, even if she thinks she has forgotten Him.

And that is the best answer of the lot, to give, I think. On a more Earth-like level, when I only finished high school at the end of 1964, before I started working the following April, in 1965, in the City of Sydney Public Library, C.S. Lewis had already passed away in November of 1963, on the same day that JFK was assassinated as well as another author, Aldous Huxley, the author of Brave New World.

Much has happened in the world since then, some of it beyond C.S.Lewis' & Aldous Huxley's wildest dreams. And if Susan was at the same age as I was in 1965, let alone 1955, she'd have a whole story to fill out at least one book, to tell the truth, that neither Aldous Huxley nor C.S. Lewis would have ever imagined. Doug Gresham even said as much when he envisaged Susan living in the United States as a great-grandmother, perhaps near Ashham? College, that college from where Doug Gresham was speaking on the 50th anniversary of C.S.Lewis' death, in 2013, which Westminster Abbey honoured by including a plaque in his honour in Poet's Corner. 

As I have mentioned earlier, another author in 2004 wrote a short story about Susan's situation, actually entitled The Problem of Susan. This short story's theme is about Susan's (likely) trauma at losing her whole family and thus being the sole survivor. It is also a commentary about the perception of casual readers of Susan's being "excluded from Narnia Heaven", when a journalist interviews a presumed Susan, a retired Children's Literature Professor, whose name had been changed to "Hastings", quite near Pevensie, in England, frail, but still very much alive, up to that point, though the stress of the interview caused her to pass away the night afterwards. 

Which inspired me to write down my own version of what I thought might have happened, when Susan still is, and always was, a genuinely fictional character, & it occurred to me, it might be really quite uncomfortable to be a real person called "Susan Pevensie", much as Arthur Ransom based one of his characters, "Titty", in his lovely series of books, beginning with Swallows and Amazons, on a very real character, along with Charles Dodgson, writing as Lewis Carroll, who based Alice in Alice in Wonderland on Alice Liddell and her sisters. But when C.S. Lewis has Aslan telling the 7 Friends of Narnia that there was a real trainwreck which killed all their family apart from Susan, herself, I thought the most likely explanation for Mr & Mrs Pevensie being killed in the same accident, was that as Aslan said, they were possibly travelling to Bristol just to meet Susan, very possibly returning from her honeymoon. That way, I thought, she'd be somewhat less bereft, if her choice of husband was up to the mark as a good husband, and a bit better than either Rabadash or Prince Caspian. 

If The Last Battle was ever to be filmed, which I somewhat doubt will happen in my lifetime, I can't think of a better way to finish the series, with Susan as a grandmotherly woman, accompanied by her adult children & maybe grandchildren, attending a 50th anniversary of that very real train wreck, similar to what we most likely will, in 2027, when on 19th January, the devastating Granville Railway Disaster will very likely be commemorated by throwing roses either on the train line or, more safely, at a service in the memorial adjoining a nearby park.