Tbf, in the first game she realize of being created to save the world very late in the game so she doesn't have this huge weight on her shoulders for most of the game.
In the second game she start the game in total desperation because the place she visit is the last place available to get some info and she is the only one who can access to these facilities, and sylens trick her multiple times, so she get even more mad (understandable, i love sylens but the dude is a gigantic cunt himself, let's be honest), and she probably never rested since the start of the first game basically, that would make anyone cranky, fight me on that.
I think people completely ignore the fucktons of factors that make her what she is in the game.
She has an extremely small amount of time to save the entire planet, she is literally the only one who can do it because she has the body and voice of sobeck to access all the facilities or give orders to the ia, i don't know how anyone would be calm, lovable and funny when you have the biggest weight in your shoulder and literally everyone is more worried about their small tribe problems or religious stuff (that she knows being fairytales at best).
Add to that the fact that she has been treated like shit for her entire childhood with only one dude being kind to her and you can kinda understand.
She has no time to be friendly, she has no time to lose in petty religious\tribe stuff, i think her being a cunt that just want to save the world is kinda understandable.
If there is one videogame protagonist that has all the reason to be a cunt, it's probably aloy.
Geralt seems bored or downright annoyed to listen at peasant (that secretely hate his kind and he knows that) problems because he is usually way smarter and knoledgeable than them (same for aloy with the tribes) and i never seen anyone calling geralt a cunt because he is not all kindness and jokes...
(Not saying that aloy is written remotely as good as geralt but you get the gist)
It feels like people who strongly criticize her have no idea of the weight and responsibility that she feels, i know that if i was in her exact situation i would be mad at people wasting my times with petty shit when i try to save their collectives asses, tell me how off i am...
I remember people being mad at her destroying the bulwark and i ask to these people, what was the fucking alternative? Wasting even more time trying to convince what is clearly a piece of shitt character that only listen to actions? The chick has a time limit and the game try to convey her desperation.