Why did Ahsoka not assist the rebelion after order 66?

With the creation of the clone wars animated series, the characters introduced became canon. So I've been wondering, after the series ended, nothing is ever heard of of Ahsoka Tano. She simply leaves the Jedi Order behind and walks off into the sunset. But what ever became of her? One would think that a former Jedi with that much talent and potential would assist Yoda and Obi-Wan in taking down the empire. So why did she not resurface after Order 66 was carried out? Why did she not help the rebels fight the empire?