H4 visa stamping in case of H1 transfer

[rks001]

Hi,

I recently went to India to get married. After marriage, my wife got her H4 visa stamped with my current employer.
After a few days, I came back to US but my wife had to stay back due to some personal work.

After coming to US, I got a better opportunity and changed my H1 employer.

So, based on this, I have the following queries.
1. Now that I have changed my employer, does my wife need to go for visa stamping again or she can travel on the existing stamped visa?
2. In either scenario(with or without going for visa stamping again), what are the additional documents she needs to carry with her while travelling?

Any references would also help.

Thanks in advance.