I have an idea I'm not sure I can write, so I'm hoping others would but here's how it begins:

-The bullying is so bad in elementary and Nana's obliviousness and innocent tactless insensitivity is of no help in the matter that one day when Fem!Tsuna fell downstairs and was dying, she snapped while breaking through her seal, and decided to pay evil unto evil once out of hospital.

- She displays a childish manner of speech and personality while slowly becoming a broken, insane little girl, but she is truly quick of thought. Rationality dominates her behavior, but there are many inherent weaknesses to her psyche caused by bullying, social ostracism, useless adults and no support at home, and inclined to pay evil unto evil while only nice to those who were kind to her.

-She deteriorates to the point that before she turns 10, she has to be in a special facility, custody taken from Nana after listening to Tsuna's tale when taken by the authorities when she caused severe injuries in school by subconscious use of flames to strengthen her body. She has a hatred of everything that contributed to her misery and tends to lash at 'faces she hates' while an innocent little girl at those who treated her kindly, thus likes her therapists and likes her padded room, seeing it as a world where people can't hurt her anymore and happily plays in there. She has bookcases, a videotape case, TV and VHS player in her room and gets tutoring.

-Her Sky Flames has one of the abilities of Flames of Night and is a darker orange in color, showing her descent into hatred and anger. She can create an energy output higher than any other Flame currently in use, thus it can easily overpower the other Flames. It causes explosive bursts of energy when used, capable of decimating entire areas in a violent burst of power, and form it into shapes and lethality levels she desires. In regards to Shape Manipulation, inspiration is taken from Nemesis of To Love Ru universe(see the manga, the anime is no good).

- She hates her mother and thought Iemitsu is long dead, and when he DOES show up, its only to seal her at five leading to her misery. On occasions he visits, she just thinks of him as some freeloading drunkard bum her mother deludes herself to be her husband because as far as Tsuna knows, her father's long dead hence her mother is single.

- She will lash out at all kids her age and younger as she never got to socially mature. She will also lash out at her parents and anyone she feels will harm her and she would know by H.I alone, and instinctively knows when to actually use fire or not.

-Whether or not she descends into Flames of Night is up to you but if she does, she'll be taken to Vendicare due to laws, but not imprisoned as she has yet to commit crimes that got their attention. How this affects the mafia is up to you.