If I would be in this scenario, first I will ask her all the fears, for what is she afraid of. I will talk to her and try to speak about her fears. Speaking about her fear may make her feel emotionally light. I would try to empathize with her and make sure that is calm.
Then I will also tell her that no body can predict the death of an individual, it is never sure that you are going to die in next four weeks. Many patients live for years with this condition, so, do not loose hope.