Just a quick thought to throw out here. Could Belle being the only non-lesbian pixie not be a random mutaion of nature?
Belle (pixie) wants the MC to find a spell that will alter her sexual preference presummably so she can wantonly immerse herself in the massive on-going pixie girl-on-girl-on-girl-on-girl orgy. This seems to be the way to have sex with Callie.
Bell said she asked the crone who admitted the spell existed but claimed she didn't know anymore.
All other pixies are lesbians, but not Belle.
Erato mentioned how she saw the pair as a couple, the crone commented on how Belle must like the MC to sill be with him.
Then the crone shrinks the MC and leaves him alone with a hyper-sexual Belle. Sex was bound to happen.
Maybe the crone cast the altering sexual preference spell on Belle, or on the flower when she was forming (germinating?) to create a pixie that would be loyal to the MC in order to assure she would want stay with him and assist him in carrying out the crone's plan.