There is some random NPC in my great hall, i can't talk to her or interact in anyway. Do anyone know why is she there? Am I missing something? Or is it just a bug?

That is an npc related to Octavia's personal quest. She should only show up after the completion of Octavia's quest in ch5 however.

Well... I'm in chapter 2 i think, and didn't do any companion quests for Octavia jet... so it's just a bug then.

EDIT:
Almost forgot - Thanks!

She's there on my playthrough too.

I thought my barony was a tad young to be attracting useless nobles.

She is there on my play too. i just finished Trolls and bam she is standing there.

I also get similar behavior from multiclassing a companion (Amiri) into a ranger.
Her animal just stands around in the depths of the court, whether she is present of not.
Even if she is, it stands in a completely different part of the room.

Overall, it seems like it should be scripted to orbit her, not me, like Ekun's pet.