Tell her there are multiple people that would like to have her job. That it sounds like to you she is unhappy and would be happier working somewhere else. Put your foot down. She will probably change her tune if she is faced with a thought of her job going to someone else. Let her know whining and complaining is something you will not tolerate. Everyone has to work for a living. Does she think she's one of the ones that has it harder than everyone else?