trying to find FL led western imperial historical manhwa

so the plot goes, there's a ruthless emperor/empress (idr which) and FL is a BLOND, STRAIGHT HAIR princess who pretends to be stupid in front of her heir siblings and everyone else so that they think she is harmless, but is actually rally smart and is plotting revenge.

she slowly tries to become the most favoured child and there may be elements of magic, but i dont think it's regression or isekai

it's a completed work and she succeeds by dethroning the emperor and taking revenge. any ideas what this might be?