Right from the airport she may have been mistreated by employees, which are all state employees still (Milei is currently in the process of dismantling that). The airport mob obliges you to their shitty services at ridiculous costs, so they treat you like their bitch. Because you (we) are.

Making the first step out from the airport gets you in the next trap which is the cab mob. Again, Milei is in the process of dismantling that too. The cab mob obliges you to their shitty services at ridiculous costs, so they treat you like their bitch. Because you (we) are.

Right after surviving that you are now in the Capital, where you are likely to encounter the infamous stereotype of the locals, the "porteño". They are used to be treated like the center of the universe, because everything was structured so that the Capital centralized all economic flow and power. So they treat everyone like "inferiors". They are insufferable entitled jerks exactly as your cousin described. The "porteño" is the most indoctrinated unit inherited from the socialist regime, and one of the things they are instructed to believe is that all and every shortcomings the regime ever had were solely caused by "foreing intervention, specially from the USA". Because, of course, socialism can never fail. So it has to be the USA sabotaging everything. So many entitled jerks, armchair revolutionaries, might be bitter to USA and UK foreigners. But apart from that, they are default bitter to everyone, specially to other Argentines outside of the Capital.

Then, if she visited mostly traditional tourist destinies, she might have been treated like shit again because people on those posts usually hold sole possession of whatever shitty service they give because they have a deal with the local govt. So it's a "tourism mob" that again, obliges you to their shitty services at ridiculous costs, so they treat you like their bitch. Because you (we) are.

That said, she was also very unfortunate. It's not that common to find a majority of jerks. She had really bad luck. There's also a common trait of the Capital and its suburbs and it's that there's so much people and so much activity concentrated in that zone that people tend to be always in haste and they are so used to it that even among themselves they don't perceive hasteful manners as mistreatment. It's just normal to them. That also has lead to a culture of hasteful expression in which people sound like entitled jerks literally all the time because it became a cultural mannerism, and they will talk to you that way not meaning to offend you at all (and I know that first hand because I have family there that sound like that but they are sweet and mellow).