Oh look, an entire 'analysis' based on false and racist, sexist fanon interpolated from characters who bully Arya as ugly because she looks different to them that will now get reblogged by the casual fans with the wrong canon that Arya is 'ugly'. This is how fanon gets formed and widespread.
In old stories, especially those that feature morality and ethics, so often the "good" characters are beautiful, while the "evil" ones are ugly.
This is especially funny because this is a fandom where a canonically selfish, classist, patriarchal, pro-status quo bully like Sansa is seen as 'good', the champion of the poor, the most compassionate character with the most empathy, the 'embodiment of hope for the future' because she is classically beautiful, fits into Eurocentric beauty standards and represents white female fragility and the canonically white Arya is headcanoned as poc because they see her as ugly, violent, impulsive, stupid, tribal, barbaric, savage, uncouth, unicivilized and unfit to have a family and love.
What you are writing here is the exact opposite of what is happening. Where, it is not the author, but the fandom that is headcanoning a canonically pretty, white girl as ugly and poc because they see her as violent and uncouth.
Where a nine year old, skinny little girl is masculinized, her femininity stripped and she is always headcanoned as bigger and being an executioner and body guard for her older, bigger sister in popular fanart. Notice also that both characters are white, but Arya is always drawn in darker shades. Again, this goes back to that concept of white female fragility which is rooted in white supremacy where a woc cannot be envisioned as vulnerable or worth protecting.
And the most mind boggling fact is that Arya is white!! But because the racist/sexist fandom want to project all their white femininity onto Sansa, this means for them, Arya has to be masculine, ugly, violent and poc.
Just looking through OP's tags for example, this is some art of how they envision Sansa in their mind:
This is one of the Arya fanart they reblogged:
Notice the difference between the so called beautiful and ugly characters for the OP? I did look back a bit of on tags could not find any art of dark skinned Sansa by herself like the Arya art above.
Like this is stuff one sees in the fandom:
Another blogger who thinks Arya is ugly and Sansa is beautiful reblogs art like this of both characters - remember both characters are canonically white in the books...
Humans unfortunately have had a long history of unconsciously assuming positive traits (intelligence, kindness, generosity, talent) of people with high levels of personal attractiveness (PA), while also assuming negative traits (low intelligence, laziness, aggression, cruelty) to those with lower PA, without any evidence of the individual's personality, traits, thoughts, beliefs, habits.
The way this applies exactly to the racism and sexism of this fandom and how they treat the characters of Sansa and Arya is amazing and and that's what's funny about your entire post. Like, this gets to the heart of all this and yet it's the complete opposite of what you are implying.
This is why despite Arya being more intelligent that Sansa, more political then Sansa, more compassionate than Sansa, having more empathy than Sansa, being the victim of bullying from her sister Sansa, despite standing up for the powerless, despite all this, the character of Arya is constantly put down as a sociopath, violent, impulsive and stupid, while Sansa is seen as the compassionate Mother Theresa, the smart politician, the only girl who can be 'Lady of Winterfell' because she's the right kind of woman.
And this is why Arya is contantly headcanoned as ugly - despite the text making it clear that she is not!! There are several characters who call Arya pretty. Are they wrong? Are the bullies right?
You mention Brienne. This is a canonically 'ugly' character who is the embodiment of GOOD. She is exactly what you are talking about. The author goes into great detail about how ugly she is. NOTE: HE DOES NOT DO THIS WITH ARYA BECAUSE ARYA IS NOT CANONICALLY UGLY. The author even has a romance arc with Brienne who is ugly on the outside and beautiful on the inside and Jaime who is beautiful on the outside and ugly on the inside, his take on beauty and the beast. This is his inversion of the traditional fairy tale tropes.
But why is Arya being grouped into this, when she has an entirely different exploration - The Ugly Duckling - of looking different, about being non-conforming, of not fitting in amongst the Tully looking Starks as opposed to the Stark looking Starks.
'LYANNA WAS BEAUTIFUL'
'SO ARE YOU'
This is right there in the text!! Again, why is this being ignored in favor of what two bullies are mocking a little girl for? Are bullies right?
How does this relate to OP's assertion? It supports it. Martin's choice to write both Arya and Brienne as physically plain at best was a deliberate choice.
Except this nine year old is not old enough or taken care of her appearance enough for us to know whether she is plain or not. We know this of the 17 year old Brienne - and the themes you mentioned are explicitly explored with her in terms of good and evil being connected to a character's looks.
And Tyriongirl should know as a Tyrion girl that if Martin wants the readers to know a character is ugly he will make that damn clear by mentioning every other page how ugly the character is which he does with Tyrion. Never with Arya.
This creates a disconnect because we are so conditioned to expect our protags to be attractive on top of everything else, that it's difficult to mentally picture them as anything but.
EXACTLY! Conditioning on top of the racism and sexism, means that white tradfems who see Sansa as the embodiment of white femininity expect Arya to be ugly, brown, primitive and violent.
And this is what is happening and this is why there is a backlash everytime there are posts like this primarily from Sansa fans about how Arya is ugly and how that should be accepted for ugly representation when Arya is canonically not ugly and there is already an amazing, great character in Brienne for ugly representation.
But the the 'ugly' discourse has never been about representation or even Arya as a character. It's always Sansa fans digging this up because they need Sansa to be special and unique and feminine and blue eyed and beautiful and romantic and lady like and they don't want Arya to encroach on all that ever.
Here's a question. Why is Jon never at the center of ugly discourse given he is older, supposedly plain looking and has the Stark look just like Arya. He and Arya look so much alike. Sansa who thinks Arya is ugly also calls out Jon Snow for his looks and her classism is on display when she thinks they are both ugly because they are bastards.
Where are all the 'Why is Jon drawn so handsome when he is ugly in the books' arguments and discourse? Why are you not writing your 'fairy tale' analysis for Jon Snow and good and bad and beautiful and ugly?
I will give you a clue - because it's never about ugly representation and instead a desire by Sansa fans who need Arya to be ugly because the bully should always be right.
It's an internalized prejudice for sure, but one that has been reinforced so many times through most every story, book, movie, TV, anime, etc. that we consume that it's difficult to shift the mental paradigm. It's not an excuse, but it's an explanation.
It's definitely an internalized prejudice for sure, one full of misogyny and racism. And posts like this that disingenuously interpret what is actually happening does not help at all in challenging these age old stereotypes of beauty, race and sex.