The the fact that she has a visa available to her is great news. Now, regarding your question:

Are you sure her last entry into the US was without inspection (EWI)?
If yes, has she been in the US (illegally) for more than one year?

If you answered "yes" to these questions, I believe she needs to make sure she has an I-601A application approved before she leaves the country.

You can also check with a different lawyer.