I want to find a manga I was reading

So I was reading a manga and forgot the name of it, I'm trying to find it. It's about a girl who lived in the streets as an assassin and died, to be reborn as a noble princess of a Duchy(?)
The Duchess is an dumb airhead and adopts a commoner with no brains, who uses her cuteness to paint fl in a bad way, the Duchess, believes whatever that girl says. The Duke is away from duchy with work(the only person with common sense)
Everyone in the manor avoids fl, which works in her favor because she sneak out of duchy to assassin people since she's doing that in this life as well

Does anyone know the name of this story?
If anyone does, please let me know