[Sangetsu]

The company won't send people who don't have any skill in English. I was reading a newspaper article a couple weeks ago, and in the article I learned that office workers and middle-management personnel from the auto manufacturers are actually required to pass an English equivalency test. I'm sure your mother will not have too much difficulty communicating with them. Just tell your mother to smile a lot, and to speak clearly and slowly, and to avoid using idioms (look it up, come down, run into, etc) if she can help it.

Tell her not to worry if the visitors don't speak very much, and to make sure that she directs her speaking to all of them, rather than just to the most senior person.