It's completly irrational, with her knowledge of her ignorance. It's entirely rational, however, given her refusal to acknowledge her ignorance until a suldam or Wise One rubs her nose in it, her patronizing attitude toward a man she once meant to be her husband (heck, even in her Accepted testing you get the sense she pins his mittens to his coat) and all the Aes Sedai conditioning not to trust any man who can channel. Maybe this is just another chance for Siuan to give her a "you're making the same mistake I did" lecture. It's painfully obvious the Light must and will destroy the old Seals before repairing the Bore, and that Egwene will oppose this as muleheadedly as ever, so AMoL may end up Cannolis favorite book when she ends up with egg on her face.

In the final analysis, she knows Rand is LTT Reborn, the strongest channeler who ever lived and graying when he died, despite never being bound by the Oath Rod. Just entering middle age, so he'd lived longer than any Aes Sedai since the Breaking, faced the DO directly and sealed the Bore. Is Egwene even twenty yet? Even if she is, is it "completely rational" for her to assume she knows more about the Seals than the man who created them?