You mean after she asked around and found out that the ONLY person who ever left the Two Rivers was Tam, and he came back with an outlander wife and child who was born elsewhere?
I mean, she followed tales of a soldier who found a baby after her New Spring list ran out. She knows who The Dragon is! The only mystery for her is why the Dark One is interested in Perrin and Mat, too.
I mean, how dumb do you think she is?