What if was something like this:
Sansa: "You're technically king now, m8."
Bran: "Nah, can't be king - I'm the three-eyed raven."
Sansa: "How do you know all of this weird stuff?"
Bran: "Three-eyed raven showed me."
Sansa: "I thought you were the three-eyed raven..."
Bran: "This old dude and me are the same person, we exist for a long time. I somewhat managed to mess the timelime and ended in the pass trying to fix everything by taunting my younger-self to a place north of the wall to learn again from my mistakes.
Damn she will never understand.
It's hard to explain."