I noticed that too I think that was probably her mother because I don’t really see her around but I also don’t know if that would make any sense either
Then there's that one panel where she says I'll ask my sister for marriage tips
I read another translator, and her sister is in marital bliss.
How that became "died unhappy", I don't know
It's almost as weird as the shine vs shi*ne thing in detective conan(￣∇￣")
"My older brother and sister are doing well"
Sister's Description: died unhappily in the Count's family