You're right, there are a lot of made up words. My comments are mostly suggestions/explanations, but you don't have to change everything according to them either.

"Trognone dans sa robe de peau"
--> 'trognone' is actually used by some people, it means 'cute'. Considering the rest of the lyrics, maybe the author also used it because of the apple mataphore, so I think you could make up a word with 'core'. I'm not sure I understand why you put 'stalkette' ?

"Un jour qu'elle était à fleur de pomme"
--> Comes from 'à fleur de peau' [highly sensitive], I don't know if it's to possible to recreate this in English.

"En tant que tarte aux nuages"
--> 'As a...'

"Elle ne séduisit personne"
--> 'She didn't...'

"She snowied glucose up to her eyelashes and said"
--> '...and said to herself'

"What good is it to slice in a rush"
--> 'How good it is/feels'

"Quickly turning her into a pathetic stalk"
--> Once again, 'trognon' is more like 'core' than 'stalk'.