I think she only suspected untill the denial,had to be certain of all three things. The red hand, fox making ravens fly, and knowing hawkwing. However, from what I remember, his memory of the horn and Falme is sketchy at best. He remembers blowing it, but not much else. Someone telling him to "play a tune to send them off into battle". But I don't recall him actually connecting that with Hawkwing from anything other then the stories of him being the leader. It wasn't untill she asked that he had visions of himself meeting Hawkwing in battle, or dieing and being priased by Hawkwing for the brilliant plans, and mentioning of fighting on the same side... possibly (and this is a stretch) Hawkwing eluding to reincarnation that is Mat and TG.

The Toy, had proven that he could lead, and is a dangerous man. I think the previous replies has done well enough to clear any misunderstandings up, but I just had to say...

After the battle, he sets her free to go back and rule, she realizes he is the one she was meant to marry, and with out knowing when they will meet again, she took her chance. Plus, it was clear she loves him, she is just a crazy bald girl so she shows it differently.