As has been established in more than one installment of Comic Book Legends Revealed (here and here, for two), Chris Claremont likes to work in the names of people he's fond of into his comics. I think it's a neat little thing he does.
However, his fondness for doing this has led to some confusion when it comes to Madelyne Pryor's origins.
Claremont was a fan of the folk band, Steeleye Span, and of their popular lead singer, Maddy Prior.
I do not believe Claremont was a personal acquaintance with Ms. Prior, but I could be wrong there.
In either case, in the pages of Avengers Annual #10 (one of the first comics written specifically to address what a writer found to be a bad story by a different writer - in this case, Claremont addressing his distaste for how Carol Danvers was written out of the Avengers), Claremont featured a young girl named Madelyne Pryor as a minor background character.
A few years later, Claremont introduced a new character named Madelyne Pryor as a love interest for Scott Summers, Cyclops.
The two characters were not meant to be the same people - just the same name. That said, I'm sure someone will ultimately come up with a way for them to be the same person. Claremont actually even joked about the confusion in an issue where he had the little girl show up again (wearing the same clothes) as a mental manifestation by Pryor, while singing one of Steeleye Span's more popular songs!
A helpful reader sent me the pages featuring that mental manifestation, from Uncanny X-Men #238 by Claremont and Marc Silvestri, as the seeds for Inferno were being planted....