Well, don't forget Lewis' explanation that the Rings only worked with respect to the Wood. They could draw people there, or they could push people away. Of course, the Wood being what it was, that was a nice capability, but that's very limited magic.
Also, the Horn was Aslan's magic. Remember that it was unpredictable - if you used it, help would come, but you weren't guaranteed what type.
Thus comparing either of those to the Deplorable Word is comparing apples to oranges. The truth is, there's nothing in the text that implies that Jadis had to go anywhere but Charn to learn the DW. Trying to infer that paying "a terrible price" meant going off to other worlds is really stretching that statement far beyond anything the plain text states.
Clearly Jadis is familiar with the idea of multiple worlds and travel between them, since she just presumes that Digory and Polly had come from another world (and were going to take her back). But there's strong circumstantial evidence that Jadis couldn't get to any other worlds from Charn: that is, her response to the aftermath of the use of the Deplorable Word. She'd just wiped out every other living being in her world. If there was a time to skip out, that would have been it. But what did she do? Put herself in suspended animation in the Chamber of Images. I'd suggest that she wouldn't have done that if there had been any other option. There was no guarantee that anyone would ever show up, yet she did it. Q.E.D. she was stuck there.