You could also combine the alone training and crating.

Start feeding her in her crate so that she associates it with a good thing...food. Practice crating her while you are there so that she doesn't instantly associate crating with being alone. (Keep a TV or radio on when you do leave so that the voices don't make it seem so lonely.) Try the leaving for a few minutes at a time like Giselle said, except the dog stays in the crate and she gets to have her kong and chewies. When you come back after the 5, 10, 15, 30 minutes and she is still in her crate have a "praise party". When she doesn't have to be crated leave the crate door open so she can go in on her own if she wants. Hope this helps.