she can work without visa stamp
she can work without visa stamp when she changes status from H4 to H1 in US, with valid and consistent I-94 number, say, in your case, entering US before Apr 1. This is like those F1-OPT-H1 holders in US, who are eligible to work without a visa stamp from consulate.
She can also go to neighbouring countries or China to get a visa stamp for H1 within 3 years. Up to her.