What happened to?

I had assumed the original chloe died??

I also assume that. But, seriously, how did she die? I need explanation and a concrete reason.

So much sadness can actually kill somebody, crying to much can cause dehydration. Though it's just an assumption but maybe she was so depressed she died from dehydration while crying? I mean It's possible...¯_(ᗒᗩᗕ)_/¯

honestly, I don't think there'll be any solid explanation. New life isekais aren't very descriptive when it comes sudden world changes. Kind of wish they'd give an explanation though. I don't mind the cliched "they both died and the mc's soul went to an alternate universe noble body" as long as the rest of the story is unique.

Yh but it is curious how she retained her memories, since its not a past life ore book or game sooo, your ideas had merit?
But yeah with the way they mishandled her care, and with her being weak and incapable i wouldnt be surprised if she died of a sudden fever from a bath too lukewarm not enought sheets or towels, wet hair, and then no one to care when she didnt leave her room? Oooorr consumption, they died of that alot in those times and it could of been festering for a while and no one would've noticed. People are known to die of broken hearts, and worrying or stress... i feel like it wouldve been one of those ways to go ya know something that could've been prevented had she just spoke up more

Since she’s kept her memory, I assumed that they simply fused and Mc personality simply came’ atop...

Somehow, I want the original Chloe to survive and live a happy life. She's just so pitiful