In "The Dragon and The Wolf" (Game of Thrones, S07E07), Cersei
1) announces her disbelief in the Night King, 2) changes her mind when she sees the wight and sees Euron flee, but it is later revealed that this was planned, 3) demands Jon remain neutral after the war against the Night King, 4) refuses a truce after Jon refuses her demands, but is then convinced by Tyrion to accept the truce, and 5) turns out to not accept the truce after all, and intends Daenerys and Jon to fight NK alone.
What are her intentions and plans throughout this interaction?
It seems very confusing to me. Her action number 1 and action number 2 seem to conflict: if she didn't believe in the Night King army, how could she have planned for Euron to pretend to betray her in the first place? If she did believe in it, why did she pretend not to?
In action (3), she demands Jon not choose sides if Cersei is to help them in the war. But, as she reveals in (5), she never intended to join them in the first place. So, what was the point of asking Jon to not choose sides? Even if he agreed, the moment he realizes Cersei's betrayal, that oath automatically becomes null, right? Because Cersei didn't keep up her end of the word, why should Jon?
Finally, Cersei's plan is to make it seem as if she will join them, when, in reality, she won't (5). But why did she agree to meet with them at all then? What is the point of pretending that she will join when in reality she won't? Even if she flat-out refused them, wouldn't the same conclusion be reached? Jon and Daenerys would march North, and Cersei would stay behind. Same result. Her "betrayal" wouldn't come as a surprise either, since Jon and Daenerys would immediately realize it upon arrival at Winterfell, where a raven would presumably inform them that hey, the Lannister army is still at King's Landing.
So did she only agree to meet them in order for this entire episode to happen? What other reasons did she have?