Ah, this is such a fascinating topic to dissect! The 'female noble 6' is a term I've seen floating around fan circles, and I think it refers to the six distinct archetypes of noblewomen you find in court intrigue novels—think stories like 'The Cruel Prince' or 'Daughter of the Moon Goddess', though it's less about a single series and more about recurring roles in the genre.
So, breaking it down, the six are usually the Queen, the Crown Princess or Heir, the Dowager Queen or Queen Mother, the Princess-consort (married into the main line), the High Duchess or powerful matriarch of a great house, and the Courtier-Spy or political operator. Each has unique power structures; the Queen holds ultimate ceremonial and sometimes political authority, the Dowager wields immense influence through her network and experience, and the Courtier-Spy's power is entirely in secrets and manipulation. Their duties range from managing households and alliances to securing succession, orchestrating marriages, and navigating (or starting) wars. The High Duchess is basically running a mini-kingdom within the realm.
What I find most interesting is how these roles often clash. The Queen and the Dowager are frequently at odds, while the Princess-consort has to balance loyalty to her birth family and her new one. It's a system built on tension, which is why it makes for such compelling drama.