Is she really awake? Or is it like sleep walking but sleep sitting instead? I can see how whatever it is, it would feel pretty unsettling!

I might guess though that as you are both so used to each other's night rhythms that maybe you are just sensing that she's awake and walking in just as she's sat herself up? She certainly doesn't sound upset or worried.

Wow it's so interesting - look forward to hearing if it continues!