https://www.vox.com/culture/2017/12/12/16762062/cat-person-e...
Quoting from that article, also:
“Cat Person” does not bear any of the signifiers of a personal essay: It is told in the third person, not the first, and it appears in the New Yorker’s fiction section, with FICTION splashed at the top of the page. Nonetheless, the default response from many seemed to be to treat it as an essay rather than as a short story.
A lot of the criticism I'm seeing in the comments here seem to tacitly be assuming that this essay in Slate is relaying facts about "Cat Person" that were known at, or shortly after, the time of publication. They were not. If anything, the assumption was that the story was somewhat autobiographical -- and from what I can see, it really was somewhat autobiographical. The character of Margot is, again, fictional, but she clearly owes more to her author's experiences than to the essayist's.
Roupenian shouldn't have taken autobiographical bits and bobs from a stranger's life, no. But do keep in mind that she had absolutely no idea that the story was going to go viral this way; it's not like Twitter is regularly aflame with buzzy conversation about the latest short fiction piece in the New Yorker. This was an extraordinary event, and like all too much on Twitter in the last few years, chiefly driven by people who decided the story was something people needed to get outraged by. And, again, their outrage was not over Roupenian's mild appropriation.