Also, my rrat is that the cab driver watches vtubers, probably Hololive, and actually understood the context of Pippa's TSKR and found it funny. He's in on the joke, I can feel it in my soul. He understood that Pippa watches vtubers, or even may have guessed that she is one but hasn't the slightest clue beyond that.
Even if none of that is true Pippa probably can't understand that from his POV a cute white girl tried to be friendly and/or funny in a scuffed way and it was cute to him. Pippa is woefully unaware that she's cute and that's why random people try to strike up conversations with her, she almost certainly radiates a friendly and welcoming energy without realizing it.