In the aftermath of the battle against the Night King, probably in the fourth episode of this season, something will happen that will cause Daenerys to call for the execution of Sansa. I'm thinking Daenerys will try to commandeer all of the remaining troops and supplies in the North in order to march south and dethrone Cersei. Sansa will refuse, of course, because her loyalty is to the North and they still need to survive the winter (even a shortened winter, assuming it is somehow linked to the White Walkers).
There will be a conflict within Winterfell, with many of the surviving characters taking sides. Arya, Brienne, Podrick, Jaime, Theon (if he arrives in time), the Hound (maybe), Sam, Lyanna Mormont (representing the North), and Bronze Yohn (representing the Vale) will all defend Sansa. Jorah will be reluctant to fight Sam and Lyanna, but he is devoted to Daenerys and will follow her orders. Tyrion will be reluctant to fight Jaime and Podrick, and he will also advise Daenerys against angering or betraying the North, which will draw her wrath upon him as well. Perhaps she will cut out his tongue, as has been long predicted (i.e., Jaime lost his sword hand, Cersei lost her children…). Jon, Davos, and maybe Varys will do their best to defuse the situation and end the conflict peacefully, but they will fail.
The conflict will escalate until Daenerys goes mad, mounts her last surviving dragon (probably Drogon, but maybe not), and begins to destroy the castle and everyone in it. Yes, including the smallfolk refugees who packed into it over the first two episodes of the season. At that point, Jon will realize that Daenerys and her dragons are the mirror image of the Night King and his wights, in that they are both absolutely destructive to the people of Westeros. Jon will kill Daenerys, stopping her madness and fulfilling the prophecy of Azor Ahai.
The "Ice and Fire" in "A Song of Ice and Fire" has two different levels of meaning. The internal/metaphorical meaning is the human struggle within Jon between Stark and Targaryen, between love and duty. The external/literal meaning is the superhuman struggle between the White Walkers and the Targaryens, with Westeros caught in between. The idea that Daenerys is just another faction in the war for the Iron Throne has been a fake-out from the beginning.