Juliet

So, believe it or not, this is a voluntary transformation.  I left out the other two characters, which would be her boyfriend, and the sorceress who's doing this.  Juliet and her boy have feuding families, and they concluded that a good way to deal with it was to turn themselves into monsters so their families couldn't separate them.

Okay, I know that's a stretch, but whatever.

Juliet, here, is now part human, part demon, and part spider, and will be for the next three or four hundred years, courtesy of the demon blood running through her veins.

Or something like that.  Cute girl, scary demon spider, and happy Halloween or something.