In the Series Finale, Sansan's Uncle Edmure Tully began making a speech and I understand that he was likely making a speech as to why he should be elected to be the King. However, Sansa interrupts him and says:

Uncle, please sit.

After which he embarrassingly and dejectedly sits down.

What I don't quite get, is - Did Sansa have some "authority" to speak to him like that? Does Winterfell rank higher than Riverrun in some way so she could say that?

I thought the houses were basically of equal stature, so her speaking to him like that is rather out of place, rude, and odd to me.

Of course, Winterfell was where the Night King was defeated, and Sansa was the Lady of Winterfell. She also was Jon Snow's sister, and clearly had been held in high regard by Northeners as a strong leader. Is it on that ground she has the hubris to speak to a fellow Lord? Or, was it indeed pretty rude but it's just that everyone else on the council likely agreed with her, so they just didn't say anything?