Jumping in, I also have a lot of BPD experience (example, a marriage of well over 10 years).

This is very BPD-adjacent. I’m not saying OP’s gf has it per se, because there is no way we can know from here, but this is definitely on brand.

If you read between the lines, the social conversation could written as this:

“Heading home, I need support”

“I’ll support”

<Doesn’t support>

<She feels abandoned, fight or flight kicks in and it turns her attachment-avoidant, results in silent treatment>

<OP gives space, which is interpreted as further abandonment>

<OPGF can’t take it anymore, and asks questions that feel like they’re out of left field because in fight-or-flight kicks in, clear thought is nearly impossible>

<OP finally gives reassurance that he didn’t abandon her>

<Normalcy continues>