Sim has grouch moodlet without grouch trait

My sim in the social media career had several sims over, because her work-from-home tasks were "be funny to 5 sims" and "level up writing skill". She was telling jokes to her guests while writing, and sometime during that activity she got the "Is this... Kindness? (from Grouch trait)", but she isn't a grouch. Maybe one of her guests was a grouch, I don't know, but if so, they should have been the one to get the moodlet, not my sim.