She'd be pissed because she's a wretched person. Everyone else has had to put aside their differences - the Aiel had to liberate the country that committed sacrilege against their magic tree, the Tairens and Cairhienin and Illianers had to put aside their enmities and work with the Aiel as well. Everyone on Rand's side has had to accept his amnesty for male channelers, and Rand himself had to give the Aes Sedai repeated amnesties after a constant history of abuse or violations of his trust and the Asha'man had to agree to be bonded by Aes Sedai to ameliorate totally unwarranted anger by the sisters over the Asha'man having the temerity to defend themselves from an illegal attack and attempted murder by Aes Sedai. The Children of the Light are even willing to countenance cooperation with channelers to fight the Dark One! Everyone has had to suck it up and work with their enemies and tolerate crap. Hell, even the bad guys! Remember what Liandrin told them? That she's had to work alongside people she would not voluntarily share a room with. It's a bit late in the game for Egwene to be finally taking in this lesson, much less getting up in the Dragon Reborn's grill about it.

The difference is that the Seanchan are not the equivalent of the Shadow. Allying with the USSR to fight the Nazis is exactly what Rand rightly refused to do when Sammael offered him a truce. In your hypothetical scenario, you are forgetting that the USSR & Germany were allies at the time. They were considering fighting the Soviets because the Soviets were allied to the Germans with whom they had already picked a fight. Contrary to the mythology of the war, largely written by the Soviets and their sympathizers, the USSR was the best friend and most helpful ally Hitler ever had. Further, the aid the allies ended up giving the Soviets was obscene, largely unnecessary and completely not reciprocated.

For Rand to give the Seanchan comparable aid and deserve that level of ill-will you describe, he would have to turn Illian, Tear, Ghealdan, Arad Domon and half of Andor over to the Seanchan, supply them with massive amounts of supplies and funds, build at his own expense, a manufactory for Aludra's dragons in Seandar, round up all the channelers who were born or had lived in any of the countries the Seanchan took over and turn them over to the a'dam. Every significant blow the Seanchan struck against the Shadow would have been facilitated by a major effort or offensive on the part of the wetlanders and Aiel, and the recovery of Malkier from the Blight would have been held up to allow the Seanchan to conquer it for themselves. Maybe if he did all that, he might deserve the anger or criticism on Egwene's part.

Egwene being mad at Rand for anything in line with what he has heretofore proposed about the Seanchan, is nothing more than the ridiculous, petulant complaints of a spoiled child who wants Rand to do her job for her. As Rand himself tells Cadsuane, its just a truce with him. Once he's done with the Shadow, Egwene will be free to fight them all she wishes. If people might prefer a competent government that actually keeps order and holds an ideal of equality before the law, well that's their preference, and Egwene has no right to demand that Rand drive off her problem for her. To suggest that the Seanchan are remotely as bad as the Shadow is absurd and ludicrous hyperbole. For someone who has not raised a finger against the Seanchan except to defend an attack on her actual home to criticize anything Rand does or chooses not to do against them is equally absurd. "Rand al'Thor, how DARE you set aside a problem I am not capable of handling on my own in order to work towards the greatest threat in the history of the world, for which you are destined by prophecy!" As if Egwene has not allowed EVERYTHING in the world to take a back seat to her own personal quest to gain power/save the dysfunctional faction that has let the world get into such a bad state from the consequences of their own malfeasance.