okay but for realz tho, in the previous chapters there was the thing about the resonance. so i'm thinking keira should have minimal or avoid having physical contact with that blonde bxtch. i might've understood it wrong (i read probably a hundred other mangas/webtoons at the same time so i might be mistaken) bc what i recall was that resonance is only for sisters. blood-related sisters. so i'm guessing since keira has yet to tap on her mana before, blonde bxtch took the oppurtunity to sTeAL her mana to be able to see spirits.
and since they're saying the other wife that duke has didn't get to bear a child, i'm also thinking that she's a lab baby.. idk it might be too advanced with the story's setting. or maybe there's an alternative to that like sacrificing something to have/create another living being?
might be digging too deep into this, i'll just try to keep this a reference. who knows i might make my own story lolololol ¯(ツ)/¯