My cousin is certified extrovert. She basically always „needs“ someone to talk to on family gatherings. I think she’s fine being alone, but if there’s a person she will talk to them.

If there’s someone telling a story and she’s not too invested she will open a parallel conversation.

Sometimes I wonder if anybody even is absolutely one or the other at all times and circumstances.

Well, absolutely not. I thought it's pretty obvious that this is more like a scale were you fall somewhere between one and the other. Also, those words don't really have any rigorous definitions.