I can't see the problem yet.
Then what should you say about succubus, a single Boss wich is never the same character in two games, should she have more presence in CastleVania story than Le Fanu's Character? Did you even read Le Fanu's Carmilla? She's like a female version of Dracula and a great character for a CastleVania
Why should Succubus be more important than Carmilla? Because in one game she was a Boss at Alucard's Nightmare and in another she was Rinaldo's Daughter? Succubus is never the same girl, is just the "Sexy, lovely and bad girl in lingiere" concept wich was introduced in Symphony of the Night.
Is not a Character, i repeat, is like a Golem or a Doppelganger.
Carmilla IS a Character, just like Elisabeth, and Carmilla Appeared in more games than the Bloody Cuntess (no matter if the game comes from Konami Kobe or Tokio, is a CastleVania anyway), then Carmilla wins.