Welcome to NarniaWeb, Kalta79!

That's a really interesting question. From The Magician's Nephew, we do get a vague idea that magic is somewhat "world specific", hence Jadis's magic not working at all in our world, and the apple given to Digory only working for his mother, and the apples that grew from its seeds weren't particularly magical. There is, of course, the "problem" of the apple working at all, but I suspect that one worked because it had Aslan's blessing, so to speak, and because the apple's nature wouldn't be changed so easily.

But I digress. For sure, we know that Mr. Beaver could still tell that Edmund had eaten her food when he came back for his second visit to Narnia, so if the magic stopped working in our world, it must have simply gone dormant as opposed to being completely gone. (Or perhaps the mark it left was more of a change in behavior and body language, much like how it seems like the "mark of a magician" Jadis refers to in the Magician's Nephew almost seems to be a facial expression.) If it had gone dormant, that might explain why Edmund took no special action to try to get his siblings back into Narnia, and in fact sabotaged his own attempts by making it sound like he still didn't believe it existed.

It's so hard to say because it's hard to tell how much of what he did might have been because of an enchantment in the food, and how much was just his own generally nasty behavior before he realizes the error of his ways. Really good question - I think you have me stumped!

I've always tended to think that some of the Turkish Delight's enchantment must have still been working when Edmund returned to Narnia and had dinner with the Beavers, because of Lewis' description of what each of the children felt when they first heard the name of Aslan. For Edmund, it was a sensation of "mysterious horror". I always thought this was a bit over the top if it were due merely to his general, childish nastiness. He might have had confused, conflicting feelings, or some sense of unease, but "mysterious horror" sounds much more intense and focussed, leading me to believe that the Turkish Delight was still having some effect.

Considering the cross-world magic in The Magician's Nephew, maybe Aslan's magic could work across all the worlds, but Jadis, having lived in only one world until very recently, hadn't yet mastered the skill. The apple which Aslan gave to Digory might not have had the power to give everlasting life in our world for the same reason that the lamppost and the toffee tree could grow in the Narnian-world soil for the first few days of that world's existence, but not afterwards: that the Narnian world, having only just been created, was brimming with Aslan's "creation energy"; our world, being a lot older, didn't have that power, so the magic was considerably reduced. If the Witch had stolen an apple from the Garden a thousand Narnian years later, maybe it wouldn't have given her everlasting life either - we don't know. But perhaps, having had centuries to develop her powers, by the time of the events of LWW, she could perform some limited magic which worked across the world-to-world boundaries.

Just my idea, of course...