Yeah, Kayla is like that in multiple different saves too. I've looked at her with MCCC, checking her quirks too, and nothing about her seems to have anything to do with a sim being frequently angry. It's weird.
I never thought of purposely interacting with her BECAUSE she's angry! And here I always have a hard time getting teens to develop Conflict Resolution, when I could be sending them to a gym to talk to someone who's usually angry.
In my current game, I actually control Thorne Bailey lol. My sim lured him away from Octavia, and he's gotten a makeover- no more man bun, soul patch, or sort-of goatee. And it seems like after you cancel Incite Cheers a few times, your sim gets the hint and stops doing it.