Step lightly around delicate flowers like the English Rose or the Yamato Nadeshiko. Their manner and appearance suggest meekness and submission and they have perfect etiquette, never speaking out of turn, their voices but an ephemeral whisper. They are beautiful things, kind and pure, clothed in fine dresses and soft gloves who hold silk fans... made of sharpened blades. In short, beware the proper ones.
Such a lady may look like The Ingenue, perhaps even purposefully, but this rose has thorns. Others may think these characters are powerless, but they know how to be subtle and operate within the means their "role" grants them. She may not ever show it publicly, but this character has a cunning mind with sharp intelligence and a strong will that won't bow for anyone. A word here, a look there, add a little subterfuge with Politeness Judo, and often no one ever finds out they were manipulated. Things they approve of always get done, things they disapprove of are somehow never accomplished. Such a character never loses her cool and can take anything life throws at her.
And should the time come to fight, she won't hesitate. She fights—bravely, courageously, and without holding back. She won't turn away from danger or pain. She'll deliver the final blow herself—with violence if necessary—but she'll always mix the violence with class.
In the Southern US, these women are known as Steel Magnolias. Beautiful, elegant, and symbols of their region; but they will take you down if you mess with them or their loved ones.
Related character tropes:
Femme Fatale — a morally ambiguous lady fond of dressing in the same fashion who uses charm and sex appeal to wrap men (often detectives) around her finger.
Iron Lady — dispenses with the silk. See also Pretty Princess Powerhouse and The High Queen.
Lady Macbeth — every bit as ambitious as her husband, and may be the one truly running things.
Lady of War — where the "steel" refers to literal cold, hard steel.
Lady of Black Magic — the same, but concerning magical powers of the offensive type.
Mama Bear — All maternal love and nurturing but the steel comes out when her children are threatened.
Politically-Active Princess — instead of resigning herself to a bargaining tool, this princess does the bargaining herself.
Yamato Nadeshiko — the Japanese concept of a Proper Lady, which has plenty of elements in common with this.
By its very nature, this trope is almost Always Female (although sometimes, a classy Crossdresser or The Dandy can also play the part, depending on the context). For the same reasons, there is no direct Spear Counterpart; the closest male equivalent is probably the Gentleman and a Scholar, who is likewise polite, cultured, and often badass without (necessarily) engaging in physical heroics or combat.
Compare Cultured Badass, More Deadly Than the Male, Badass Adorable, and Kicking Ass in All Her Finery. May overlap with Girly Bruiser, but not necessarily. Not to be confused with Nothing Up My Sleeve where silk sleeves are used to hide steel weapons, but there's definitely some overlap.
For "Steel Hiding Silk", see the classical variety of Tsundere, or, more literally, Samus Is a Girl; Bruiser with a Soft Center is the gender-neutral opposite.
