Oh yes, "The Girl". For some reason I am really hot for her. There is some sexual nuance in this film that conventional porn just can't touch. (Is it the mystery? I don't know.)
Perhaps it's the way she dresses.
Then again, maybe not.
But anyways (before I start panting) I think the Girl is a minion of Satan rather than Satan himself (herself?... wtf). I actually found
the script and it leaves me equally clueless to the ending.
I think the clue is in the Ninth engraving. Remember that Balkan sent the Barroness a postcard which Corso (Johnny Depp) found in her copy of the Nine Gates. On the postcard is the castle which they go to at the end.
Balkan's Ninth engraving was a forgery which if you actually look at it, foreshadow's his end.
I also think that image of the woman on this forgery is closer to appearance of the Telfer woman than that of the Girl.
The real Ninth engraving has the image of The Girl on it. It also has an image of the Castle on the postcard that Mr. Corso disapears into at the end. Note that in the actual script, he doesn't disappear into the castle, but rather just walks down some alleyway.