Kate McKinnon is a horrible person IRL as well. I know writers who worked with her and she counted how many words she had in SNL skits and threw a tantrum if she didn't have the most. She also would demand more update characters and frequently said things like "people only watch this show for me " during rehearsals. This is how she ended up doing the Hillary "Hallelujah" opening and why she played RBG so often. Her jealousy is also why Lorne started using older outside performers like Alec Baldwin for weekly roles because she didn't complain about them.

She would also undermine other less confident performers by pulling a face whenever anyone else spoke to try and steal all the attention she could in the scene. I'm always surprised more people didn't pick up on her doing that.

By all accounts she was intensely disliked (idk if she's still there) by everyone except Lorne.