Our heroine is a tomboy — rough and tumble, as interested in fashion as she is interested in watching paint dry. However, in the reboot or in the doll, she becomes a girly girl. Often complete with princess dress or at least a Pimped-Out Dress, tween fashion and long hair, often with hair decorations.
Notice that the girl is often aged up — from little girl to tween. (Ironically, tweens are often less feminine than little girls — tweens are at the stage of life where the dresses and cuteness are ditched for a more mature style.)
Compare/contrast Fan Service Pack. See also Chickification.
Unlike Chickification, this trope doesn't necessarily mean she becomes weaker. The trick is that the girl becomes more dainty-looking, but keeps at least a good part of her core personality underneath the skirts and make-up. Bottom Line: this trope and Chickification DO NOT OVERLAP, so take any examples of Chickification to the page itself.
If becoming girlier is portrayed as better or worse than being more tomboyish, then you've got some Unfortunate Implications on your hand. Almost always overlaps with Hotter and Sexier.
An interesting variation occurs in the manga Ice Revolution when karate champion Masaki arranges her own Girliness Upgrade by switching to figure skating, which she views as a prettier, more feminine form of athleticism. She manages to secure her macho father's support only by proving that a "girly" activity like figure skating is a physical sport every bit as demanding as karate. (And it is.)
Happens to Itsuki in HeartCatch Pretty Cure! as part of her Character Development. She starts out hiding her love of stuffed animals and desire to doll up in cute clothing behind a masculine exterior, out of a desire to be a respected martial artist like her Ill Boy twin brother Satsuki. After joining the Fashion Club (and later, becoming a Cure herself), she learns that it's alright for her to enjoy both martial arts and cute things (helped by how Satsuki is operated on and begins to physicaly get better), and eventually she grows her hair out a bit and starts wearing the female uniform during the finale.
Fairy Tail: Mirajane underwent this process before the story begins; Lucy is shocked to learn that Fairy Tail's resident Team Mom and Yamato Nadeshiko used to be bitter rivals with BadassAction Girl Erza. It's explained that this happened due to the disappearance of Mirajane and Elfman's younger sister, Lisanna.
Ami in Sailor Moon was always portrayed with Boyish Short Hair in the anime. In the live action her civilian self has long hair and, while her Sailor costume has the short blue hair, it's in a much more feminine style than the anime and manga. Ami's character also gets upgraded from just The Smart Guy to also being The Heart as well.
Takatsuki from Wandering Son was treated as a transsexual boy for most of the run. They showed disdain and general dysphoria for feminine things such as skirts, dresses, and being treated like a girl. Part way during high school they become a female model but they start off as androgynous. Eventually Takatsuki grows their hair out to longer than it's ever been depicted, begins wearing girl's clothes, and shows signs of not seeing themselves as a boy anymore. Eventually they decide not to transition and lean more toward Girly Girl than Bifauxnentomboy.The fandom reacted about as well as you'd expect.
Most her dolls are wearing the silk blue dress. You know, the one she hated for being painfully restricting and impractical.
In Up, Ellie appears much more feminine during her adult years than during her childhood. Doesn't stop her from being charming or Adorkable, however.
Scarlet from The Ultra Violets gets a very minor one in book 2, Power to the Purple! She begins wearing a tutu with her rocker shirt, wears ballet shoes with pride, and auditions as Little Orphan Annie in the school play. She's also much more comfortable with her dancing superpowers. She can still and does beat the crap out of bullies, though.
In Smallville, Chloe gradually goes through this in season six and seven, ever since she starts dating Jimmy Olsen. In worse episodes it borders on Chickification. Like the opening scene of Quest. Sleeper may count - fans seems divided on whether it is So Bad, It's Good or is a one-episode Dork Age.
iCarly devoted an episode to this, with Carly trying to help Sam become more girly. She was back to normal by the end of the episode, because Status Quo Is God.
Also inverted it in an episode where Carly tries to stay with Spencer. Carly turns herself into a punk chick with full black clothing, metal spikes and chains, and a streak of blue hair.
Hannah Montana generally did this to Lily as the show wore on. When she first showed up, she was a skateboard riding tomboy, by the end she's as girly as Hannah.
Claudia Brown on Primeval mostly dressed in business suits and casual clothes. Her replacement (long story) Jenny Lewis (notthat one) arrived always wearing full makeup, the latest fashions and high heels. Subverted in season 3 when Jenny starts wearing more practical clothing. Subverted again when we see her in season 4 and she's back to wearing dresses all the time.
Skins seems to be headed down this road with Franky Fitzgerald, despite the fact that much of her previous acclaim was due to her uniqueness as an androgynous female character who still attracted male attention. It's not helped by the fact that the show's explanation is full of Unfortunate Implications about her "growing confidence" automatically leading to girlier clothes, and it's come with personality changes, too (becoming much more self-centered and flirtatious than she was in her previous series).
Played with in an episode of Laverne and Shirley where Laverne tries to attract a guy by dressing and behaving in a more feminine manner. It doesn't change who she is inside, and she ultimately decides she would rather be herself.
Patricia on House of Anubis. She's the cool goth who says what she thinks, does what she wants and scares the rest of the students in all three seasons, but come season 2 her personality started to soften up overall. What happened? Well, she met Eddie and started to turn a bit nicer.
Not to mention the whole near death mystery stuff and the power of friendship. If those things can't begin to chip away at someone's icy shell, nothing can.
One Tree Hill did it to Peyton, Brooke & Hayley between seasons 4 & 5. Rather than being done to make them more feminine, it was instead done to show them as more mature than the prior season due to a 4 year Time Skip.
Rachel Stevens commented on this after she began her solo career. She remarked that in S Club 7 she had mostly worn jeans and t-shirts in her videos but wore much more make-up and feminine outfits in her solo videos (not to mention getting a lot more provocative).
In the beginnings of Girls Aloud's musical career, they were dressed in fatigues and tomboyish clothing. As their singles progressed, they began to wear more make-up and feminine outfits. Compare their images in "The Promise" to "Sound of the Underground" and the difference is astounding.
Chyna already had gone through plenty of Fail Polish by the end of the year 2000. Then all of a sudden when she entered the women's division her ring gear became more feminine and she lost weight as well as wearing dresses and high heels backstage.
Natalya Neidheart suddenly got very pretty at the end of 2010 where she was seen dolled up to the nines any time she wasn't wrestling. Her partner Beth Phoenix got in on this around mid-2011.
Kit of the American Girl doll line is mentioned to despise pink and, in the books is the Tomboy to her best friend Ruthie's Girly Girl. For the most part, her line has kept this, but when The Film of the Book came out, her blue school outfit and pajamas were both slowly phased out for girlier, pinker outfits that would be much more in-character for Ruthie to own... despite Ruthie herself getting her own doll and line of clothes.
Troll Dolls- cute gender neutral toys have now become fashion loving tweens called Trollz.
Kairi from Kingdom Hearts is rather tomboyish in the original game, but becomes more feminine (with longer hair, a pink outfit, and whatnot) when a year passes in Kingdom Hearts II.
Brigette, the young host of Pokémon Box Ruby and Sapphire, used to look a lot more like a tomboyish teenage girl in her first appearance, as she had short hair, a Dangerously Short Skirt, and brown sandals. When she reappeared as the host for Pokémon Bank, she was given a more feminine redesign, with a dress, longer hair, and girlier green sandals; she still looks a bit like a tomboy, but far less so.
Rainbow Brite: Rainbow Brite's 2009 doll redesign includes thinner waists, longer hair, and more sparkle. It unsurprisingly bombed and only lasted a few months in stores.
Dora the Explorer: Princess Dora doll, and new Dora dolls that feature an older Dora with longer hair, a headband, a dress, and tights. Although it's not unreasonable, given that she's now "Tween Dora" and has aged a few years.
Strawberry Shortcake: Updated from a round cupcake country-cottage look to a cute tomboy to a long haired strawberry blond tween.
My Little Pony Equestria Girls went this route, most infamously with Applejack and Rainbow Dash. Despite the many cries of Ruined Forever, their personalities and roles remained pretty much the same as their pony counterparts.
There was an attempt to do this with The Powerpuff Girls a while back. They did the standard Girliness Upgrade: Make the girls taller and skinner, had them wear makeup, gave them "girlier" hair. These versions were placed on things like makeup bags, and they had more emphasis on "girly" activities like shopping and makeup. It didn't seem to stick although it's hard to find anything on the internet regarding that. For reference, here's the◊ redesign.
This was parodied in a timeskip episode where the girls grow up to become shopping obsessed valley girls. They end up trying to hit on the Rowdy Ruff Boys when Townsville is under attack.
Gwen from Ben 10 was this after the time skip. Her original series incarnation was a sharp-tongued 10 years old smart girl with slightly tomboyish characteristics (mainly martial art skills, short hair, and temper). Her Alien Force incarnation, while retaining the intellectual personality and remaining a competent Action Girl, has an obvious more feminine appearance, is less of a Deadpan Snarker and more calm and responsible (at least in the first two seasons), becoming something of a Team Mom, and has a All Girls Want Bad Boys relationship with Kevin. In some episodes she is pretty much just a Satellite Love Interest to Kevin.
Opinions vary on whether this is for better or for worse, as her lack of wackiness was considered extremely out-of-place by some viewers of Space Jam, and she was something of a Flat Character.
Invoked in the Mike, Lu & Og episode "For the Love of Mike". When tomboy Mike's increasingly dirty methods of trying to keep Haggis and Baggis Cuzzlewit away only make them more attracted to her, Mike decided to do the opposite and girls herself up with a pretty dress, lipstick and perfume. It works.
In the mid-2000s, Disney Channel gave Spinelli, the tomboyish female lead from Recess a big of one when she appeared in promos for the show. The advertisements only featured her, and she spoke like a borderline Valley Girl. This also happened when Disney Channel was going through their own girliness upgrade. This version of Spinelli went as quick as she came in.
Joan of Arc's image in media is often given this, portraying her as a Lady of War and often with long hair. In reality, Joan was a downright Sweet Polly Oliver who wore men's clothes for several reasons: not being seen as inferior by the troops, not having privilege over them, avoid possible rape attempts, etc.
In some ways and circumstances, most 1920s flappers evolved into 1930s sirens. The same way could apply to 1940s workwomen evolving into 1950s housewives.