>>532293674
She's the only spellsword character in the game.
In Elden Ring you could play all casters like her, but in Nightreign you either go full melee + Ironeye or full caster.
Duchess is the only one who can effectively do both, which gives her the most build variety.

I'm actually surprised that there's only one hybrid, I'm fully expecting all or at least most DLC characters to also be hybrids since most single attribute archetypes are already covered.