In the context of the story, she could have kept them from bringing *in* the Trojan horse, of course. But you're right that the point of prophecy in mythology is pretty much that no one will ever listen. No one listened to Teiresias either, and he wasn't explicitly cursed.

Or rather, no one listened to Teiresias in any of the stories we *remember*. I guess that's the subtle difference.

I used to wonder why she didn't lie too, but then I realised the point of mythology isn't character motivation. You can keep asking "why" a person does something, and that's not really the point. The point is the events. You kind of have to reverse-engineer yourself from English classes.