rather than her not being of this world and not having mana therefore not being eligible for the monsterification process (almost definitely happening next chapter), i would kind of rather that it technically DOES work, but given it has to "suit" the wielder and ginko is basically already so deranged and born to kill as is that changing her body into that of a monster doesn't do anything (ie. she's already a monster), something to that effect. it's a small difference but i would be more hyped with the witch going "oh i'm so fucked" than the witch going "oh no mana, duh"
i do kinda wanna see what the artist is cooking with a potential different ginko transformation though
aaah so want it done metaphorically ?
both trope already been done few times on other work and in this case 100% the correct way for it to be literal.
ginko doesn't have mana, Perfect bitch can manipulate anyone with mana. so it doesn't make sense since the setup are clear its about mana
it's like saying " you'll regret this and i'll bath in your blood when im done" but the creature you said that to are made of wood and doesnt have drop of blood in it.
different story if the setup was " i can make anyone turned into monster as long the ritual/seal are completed" then it doesn't work because ginko already a monster in a sense.
but the setup are about mana so the author clearly want to make Ginko as achilles heel of the witch