My wife is currently going through Penn Foster's Catering course (she writes the "My Penn Foster Career School Experience" blog here at eLearners), and she enjoys it quite a bit. What she found most surprising is that even though she has several year's worth of experience in the restaurant industry, she has still learned a lot through the course.
In the restaurant business, experience counts for more than anything, so if your wife can get a job in the industry while going through the course, that would probably help her chances quite a bit. I think you also got some good advice previously. Have her check around and see what potential employers say.