Azula's firebending style canonically designed to be different than most firebenders. A direct quote by Sifu Kisu himself. “Azula we took from the chaquan system.” while other firebenders use Northern Shaolin.
While Azula does use Northern Shaolin (especially in her younger self in Zuko Alone) there is still the chaquan element in her style that other firebenders weren't shown use it.
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