My mother was super passive aggressive. I grew up to consider it normal and it took me a while to see ot for what it is. Just like you describe, her style was a friendly demeanor coupled with acid remarks. And the remarks were absolutely on purpose, I know this because she would often tell me how smartly she gave so and so a comeback and so on, and how they felt ashamed but didn’t say anything back at her etc etc.

I was also on her line of fire sometimes, oh boy. It was so tough to recognise it but once I did I stood up against it. Whenever I see people behaving like that on a regular basis I just try my best not to interact with them.