invalidation of the bullying sansa subjected arya to “because they’re sisters! it happens!” displays a fundamental misunderstanding of what a ~friendly sibling rivalry~ looks like. the emotions you feel as a child when a sibling bullies you are very real and very hurtful. making fun of their appearance and making them feel like they don’t belong are things that bullies do. as children we may not be compassionate enough or thoughtful enough to dial back insults, but we do know the difference between a friendly interaction and one that’s meant to hurt someone. the bully knows it, and so does the bullied. this is how relationships between siblings are damaged early on, and while they are not impossible to repair later in life, the emotional damage that results from it is real and should not be dismissed.

if you’re curious as to what an actual friendly sibling rivalry looks like, look to jon and robb. jon describes robb as “his rival and best friend and constant companion”; he implies that they were competitive when it came to practicing swordplay, and that they each challenged each other. but this doesn’t sour their relationship because they are good to each other, they love each other, and they have no desire to make the other person feel bad about themselves. 

while there is certainly something to be said re: why GRRM chose only the sisters to have a bad relationship, this doesn’t excuse sansa’s behavior towards arya, which was nothing short of unkind.