Of course, in order of the books being written, when TSC was being written Lewis had not yet come up with the backstory for Jadis. So, at that time, it was reasonable to say that a number of witches had come out of the north. With the writing of TMN, and the revelation that Jadis actually came from another world, that raises the question about where the Green Lady came from. Is she also from another world? Or was she native to the Narnian world? Like Jadis, she seems to have been a very long liver. But then TMN explains Jadis's long life in terms of eating the fruit. Did the Green Lady also eat this fruit? Or is she just naturally a long liver? Or did she gain her long life by some other means? Would she have died naturally at some point if Rilian hadn't killed her?
In the absence of a backstory, we can't say much except that, from a face-value reading of the Chronicles, it does not seem that the Green Lady was the same person as Jadis. She could well have come from another world. Though the Jadis backstory simply transfers the issue of how a witch might arise in Narnia to how one might arise in Charn. Is there a reason one couldn't arise in Narnia? How do witches come to be? Did Aslan create them, or do they arise spontaneously? (Same question for all the nasty creatures that follow the White Witch in LWW.)
All told, Lewis really generated more questions than answers when he wrote TMN!!
Peeps
