People didn't like her in the movie because they didn't understand the human side of the story. They went in expecting dark, foreboding horror and got horror art instead, and it annoyed them off because they didn't understand it.

There's some issues with the film here and there, but I overwhelmingly loved NOPE, and the entire cast killed it, especially Keke. It's hard to tell a story in a horror film about a girl who has been hurt so deeply by her father that it has effectively stained her interests in everything else in her life, pushing her to just becoming a flighty self-promoter, and it's hard to act it out when you're competing with the Big Bad Villain. But here, it worked, and a large part of that is because she is an extremely talented actress.