What made them think she’s cursed?,the accident isn’t even her fault

It's all the idiocy of the father.
He was in love with this wife (I think) and she died giving birth to her... So of course he blames 'the person that took her away from him'.....
So yeah, everything is just bc of that father

I think. I don't actually remember if the mother died at childbirth(I might be getting hugely confused with other mangas) , or some other accident? But yeah in the end the father is blaming the FL for his wife's death