Arriving US on H4, even after approval of H1B

Hi,

My wife was in USA on H4 since May-2014. We have applied for her H1B on 1st April 2014 (when she was in India), which got approved recently (in November-2014)
We recently came to India and will be heading back to the US in Jan-2015.
Is it possible for my wife to now travel in existing H4 stamp, as she will not be currently working in the US till Mar-2015, and later start working after march (as the H1B is already approved)? Please suggest.

We are diligently looking for some legitimate options to move further.

Thanks in advance.