In fact, I find her character one of the most believable. For so long, she has been taking control to fix problems in the world, because without her intervention they tend to linger. Then a 20 year old boy from a country town turns out to be the Dragon Reborn. She naturally wants to control him because up until ToM, he acted like a child (though this is understandable) in many ways. Now that he has matured, she can understand him far better and can finally start to trust him.

It's actually kind of funny, because we are positioned to worry about Rand trusting or not trusting others, but the underlying issue behind that was really that he never gave others reason to trust him. Now that he is doing so, he is starting to find allies in the more genuine Randland characters. Characters who are still suffering control/power/trust issues like Egwene and Elayne innately fear him, but more balanced characters return his trust.