H4 to H1B Timeline Premium Processing -I140 already approved

[nri1980]

Hello friends -

My wife had a COS from H1 to H4 earlier this year. While she was working she had her I140 approved & the company has kept the GC active.

I had a question - how long does it take for the employer to file for conversion from H4 to H1 - the reason for the question is that they want to the soonest she can start working.

I was told that she can do a COS (change of status) -- not sure if you can file a premium processing. Can somebody provide me the link for the steps required by employer to file the COS

Thanks!