A Butterfly Effect

"A butterfly flaps its wings in Brazil and a tornado brews in Texas. A simple choice: Today or Tomorrow? Conceived a day earlier, the Boy Who Lived was never born. He wasn't even a glimmer in his parents' eyes."

"But she was; Harriet Lily Potter... Harry; the girl that grew up in a cupboard; the girl with safety-pinned knickers; the girl that was never wanted by the only family she had left; the girl that would give anything for the slightest bit of love."

"With a lightning bolt scar, her mother's face, and her father's messy hair, Harriet Potter has always been far less than welcome in the Dursley household. Ten years old, unloved, and uncared for, Harry has already seen more hardship than most will see in their entire lives. In fact, her life can't get much worse. Yet on July thirtieth, a strange letter is pushed through the Dursley's mail slot, turning her miserable world upside down. Discovering her magical heritage, Harry finally finds a place to belong and, after a chance meeting in a train station, she just might have found someone to love her."

"What happens when the shoes of a hero are filled by the feet of a heroine? How does the world change? How do relationships change? How important can one person possibly be?"

"Follow Harry down the familiar path. Follow her as she steps off it. Walk with her as she creates ripples of flux that grow and twist into massive tsunamis, changing the course of history as we know it... for better or for worse."

A Butterfly Effect by SlyGoddess, is a Gender Flip For Want of a Nail Harry Potter fanfiction epic that stars Harriet Lily Potter, the Girl-Who-Lived, and fleshes out JK Rowling's universe while skillfully avoiding many of the common fanfiction pitfalls.

A Butterfly Effect provides examples of:

 * Backstory: Albus Dumbledore and Gellert Grindelwald.
 * Badass: Many characters, on all sides of the morality spectrum. Understandably and realistically, trained and/or skilled adults regularly put even the badass children/teens in their place.
 * Bi the Way: Both of the main characters were declared Bi early on, and is self-admittedly Bi as of chapter 17.
 * on the other hand is still in denial about her attraction to, so much so that she actually.
 * The Chessmaster: Many characters. On a literal level, Ron and Dumbledore; Harriet is also quite good, though still not quite as good as Ron, even at her best. Yes, this often leads to a Thirty Gambit Pileup, for better or worse.
 * Closet Key: Marin has a reputation for this.
 * Doomed Protagonist: is clearly going to die at the end of the series and yet somehow, there is still supposed to be a happy ending.
 * Considering how the canon story ended, it isn't that hard to imagine ways for
 * Equivalent Exchange: Incorporates a dark, 'Fullmetal' element to the magic of Alchemy.
 * Evil Counterpart: Though they're never actually shown to encounter each other, Herpo the Foul is arguably this to Nicholas Flamel-two impossibly old, quasi-immortal wizards who have a massive influence on history under various pseudonyms, teaching powerful figures of legend the craft of magic.
 * Gayngst: Plenty.
 * Girls Love: The beautifully crafted backbone of the story. Other relationships (notably Ron and Hermione) are just as well done, and almost as prominent.
 * Glowing Eyes of Doom: first impression when she sees  eyes, though it quickly becomes But Your Wings Are Beautiful.
 * Hidden Depths: Nicholas Flamel is made into an intensely intriguing character.
 * I Just Want to Be Normal: Harriet detests the dark magic she is privy to and hates herself for using it, despite these instances often being out of her control.
 * It Got Worse: As memory serves, there is only one chapter (sans the prologue and short interludes) where none of the main characters are seriously injured, nearly killed, tortured, maimed, sexually assaulted, or worse. And that's just the characters.  To be fair, almost every chapter is over 20,000 words in length, covering a vast amount of other material. This is a Hurt Comfort Fic taken to near-extremes on both ends of hurt and comfort. As such, it can be difficult to adjust to, but it can also be extremely enjoyable.
 * Kangaroo Court: A rather infamous example; the Wizengamot is several times worse than its canon counterpart. It skips past "farce of a trial" and goes straight into "they're all complete morons with no self-respect, integrity, or care towards their own traditions, rules, morality, or curiosity." Thankfully, Dumbledore arrives, points out how insanely stupid they all are and the entire basis for the trial is in less than ten seconds, and they reluctantly rule--unanimously--that  isn't guilty. No, really. He talks for ten seconds, presents no new evidence or information, and the Wizengamot completely reverses its ruling from "A Fate Worse Than Death" to a unanimous "clear of all charges". You can't even blame this one on Adults Are Useless or pure corruption, either. In a story where almost everyone is a rounded, fleshed-out character that has actual realistic motives, this instance is bizarrely out of place and nonsensical.
 * Lipstick Lesbian: Both Harry and Ginny fit this role, with Ginny being dominant and Harry being sub (though they do "switch" sometimes, depending on the circumstances). Emotionally (and in terms of the overall relationship), Harry and Ginny normally avoid any sort of dominant and submissive roles, though Ginny's brash, stubborn, and headstrong personality do come into play.
 * Love Dodecahedron: ... and that's all by the end of 3rd year. This gets largely resolved and simplified by the end of 3rd Year, though whether or not anything will complicate it again remains to be seen.
 * Mind Manipulation: Plays a much more prominent role than in canon.
 * Necessarily Evil: ... who is surprisingly endearing and yet totally despicable at the same time.
 * This is also how Dumbledore describes the Dursleys being forced to.
 * Noble Bigot: Draco Malfoy is still a jerk, but he's a helpful jerk that tends to do the right thing in the hopes that he will someday get into Harriet's pants.
 * Round Character: Canon Ginny is somewhat flat in terms of background and personality, whereas 'A Butterfly Effect' Ginny is detailed and believable. Dozens of characters also get this treatment, from Dumbledore to Lavender Brown.
 * Serial Escalation: The power levels of some characters. Think Harry is powerful? Nah, she's  Thankfully, though, it's presented as foreshadowing, exposition, or mythology-level storytelling instead of a cliche drama-producing tool.
 * Sliding Scale of Alternate History Plausibility: Roughly Type 2.
 * Smells Sexy: Harriet and Ron really like the smell of strawberry (Ginny) and toffee apple (Hermione), respectively. To a lesser degree, Hermione and Harriet enjoy the smell of grass (Ron) whereas Ginny and Luna enjoy the smell of pine (Harriet).
 * Sugar and Ice Personality:  is the end all be all of Alpha Bitch Tsunderes. She has the rather miraculous and vastly entertaining ability to oscillate her behavior patterns between those of a full-blown Ice Queen and those of a consummate Princess Classic.
 * The Power of Love: Considerably more awesome than in canon.
 * Transparent Closet: attraction to  seems to be headed this way.
 * Unresolved Sexual Tension: All of the main characters at one point or another.