Could you tell me how you're gonna change their voice to female voice?
It's easy enough to hit newgrounds and find a voice actor to do the very short and simple script found in the game. You could probably do the entire script in a single take it's that short.
Or just use all text instead which wouldn't really take away much given the seldom used voice acting in castlevania games.
Or an even more abstract approach would be to use software to shift the pitch of the existing voices to sound feminine.
The real issue though is finding a sprite set for a character that was only done once on a very very limited hardware set and in gray scale. I think I might look for that sheet also since I was just wondering if I would be able to color and extend the existing gb set.
EDIT: I did find it. I think I might take this sheet and extend it. If I get that done I will post it up in the sprite thread and link to it here but expect a wait since it takes time and I am busy with a lot of other things. I will try to squeeze it in fairly soon though.