She would be a main character, but not a protagonist, if her story involved a massive fall into evil.

As for our supposed knowledge that Rand MUST break the Seals... I'm confused. What makes you think this? The only reason Rand thinks this way is because of Herid Fel's note, and his books, which were conveniently left behind after the Shadow went through an elaborate assassination to silence him. Both those sources are of doubtful provenance. In person, we have this:



I'm not saying any of this proves Rand is wrong. But the timing of Egwene's Dream about the Seals, added to the Pattern allowing no one but her to speak to Rand in the Hall (while the same effect was certainly not true outside, before he came in), certainly points to something at play here. Likely, they both have parts of the puzzle. The Seals do need to be broken, but only just before they can Seal the DO back again, not before they even have a plan. Likely, that is precisely what Egwene's position ends up being once she can work out the meaning of her Dream in the context of what arguments Rand offers towards the breaking of the Seals.