Lets understand the FUNDAMENTAL meaning of Change of Status.
You have to be in ONE STATUS INSIDE USA to apply for Change Of Status.
In otherwords, you cant call any process as Change of Status which you have iniated while being outsider of US.
Having said that, She can come to US on H4 status any time. If she is inside US AFTER Oct 1st of 2015, after arriving, she can apply for her change of status from H4 to H1. At that time, she doesnt need a H1 stamping to work. She can continue to live in US on her changed H1 status.