Need help figuring out if a aprt in my story is to out of left field or just really wierd

Hi folks! So I'm having a bit for trouble figuring out a major plot point for my story. I am wondering if I could bounce off an idea that may seem either to far fetched or just flat out not make sense.

So, for context, my story is about a girl who reads books about mythical creatures. Once her father learns about this he decides to send her to an insane asylum because mythical creatures are viewed as bad in their world. The MC gets saved by a fae and the story continues on with several different points and adventures.

Originally I wanted the MC to be something like a changeling but after research and much debate that hasn't worked out. My second option was to have the MC only be half fae but the MC's twin sister got in the way of that idea.The twin sister is someone I have to be a major part of the story for several different reasons. Originally when making the story the twin sister was a plus for many reasons but now I cannot figure out the MC's birth. (I don't know if you can tell, but I don't want to get rid of the twin sister)

So, there is an option that I want to know if people find interesting or intriguing or rather very idiotic, feels fandom, or just not scientificly correct. Even though the story has folklore basis I want it to be able to make since and not feel like everything is random and made up. : What if female fae are similar to female cats? This is... odd and kind of gross in a way. So female cats have the ability to get impregnated by several different males. So with this point, I was thinking I could have a lore part in my story we're a fae can denounce their faeship. The MC's mother would run away with a human without knowing she was already pregnant with a fae she was in an arraigned a marriage with. After denouncing her faeship she would marry the human she ran away with and be impregnated again and now have two children in her womb. The MC's twin is meant to be 100% human, so with this point, I could make it possible that the MC is fully fae.

Does this make sense? Would anyone hear this part of the lore and DNF the book? Like I said in the beginning, I don't want the idea to seem random and not well thought out. I also don't want to take folklore and fully change the script of it at random. Is it way to far fetched? Really wierd, gross, or feels random? (Also sorry for the long post I'm really passionate about this lol)