If she still qualify for greencard, she can re-apply a greencard again. I had the same situation before. My first greencard expired after I went back to China for over a year. I came to US with a student visa again while applying for a new greencard from China. But had to go back to China to finish interview process.....
Don't know how she got her greencard before. But I did ask a Senator's help for communication with embassy in China. It worked. She maybe give it a try....Don't hurt, right?
