My adult sim took her boyfriend, her teen daughter, and her daughters best friend camping. It was my first time playing Granite Falls, so was scrolling around looking for the supply store. Then I scrolled back to my sims, thinking the teen sim was just chatting to my sims boyfriend. But I could see by the animations that they were flirting with each other! By the time I clicked on them, they had finished. So not sure who was flirting with who, but she was a teen and he was an adult. Haven't seen it happen again, though.
I also noted that the "boring" conversation is popping up before they even speak! My sim's child daughter decided to talk to her mum, and was making her way downstairs, and it said boring conversation!