There are invariably difficult people at work—at every workplace—without fail. The problem here, as at so many places, sounds like it is lack of good leadership, which would be watching and making sure that everyone works essentially the same amount. So, there is little to do. The only recommendation would be to suggest that she make friends with the person who is working less and gossiping, just to see that this person is also human, has reasons for what he or she is doing, and might even change behavior if befriended. Otherwise, I don’t think there is much to do. Although I will watch for other responses and see what others suggest.