Looked to me like that was a flash back from when she wasn't quite a Faceless person and was being chased by her nemesis - the older young woman. We all know how that ended.
That happened all the time in the age of antiquities. Pharaohs would marry their siblings, likewise in a lot of other cultures - to keep the Royal bloodline pure.
Thank you so much. We all owe you a debt of gratitude because now we don't have to actually watch these shows.
The shows are ahead of the books at this point. Winterfell will fall. It's the northern most post in the Kingdoms. It has to fall. Question is will the Night King bring back the dead Starks to join his army?
Remember, the Wood Sprite people created him who was JAG by killing him with Isinglass to protect them from "man." They're a bit like werewolves. The one who kills and resurrects the zombie controls them, and when it dies - they all do. There's only one logical conclusion to that plot line. It's the zombie apocalypse until the Night King gets it.
Arya's dagger will be put to good use, no doubt.