First of all, you need to assure her that you are always there for her. A lot of people avoid meeting friends, after knowing about their problem. It is not a good thing to leave your friend alone. Loneliness actually makes things worse. Since she is under terrible mental stress, she may take a wrong step, after getting isolated.
You don’t need to prepare a speech to make her realise that you are there for her. Even if you don’t have anything to say, just make her feel how much you care. Stay with her, and she will surely feel comfortable after sharing some quiet time with you.
Try making her speak. It is not a good idea to deliver a speech about the decease and its effects. You should actually listen and let her talk.
Don’t put too much burden on her mind by giving a lot of advises. Even though you are worried about her, you must not make her feel uncomfortable at any stage.
Another good thing to do is going with your friend to the doctor. Since she is really upset, she may miss a few important advises from the doctor. Therefore, she must be accompanied by someone, who can take notes or ask any important question.
Keeping up communication is another good idea. If you are unable to visit her regularly, make a phone call or leave a text message.
Ask other common friends to stay with her as much as possible. An upset person may miss the regular dose, thus there must be someone around to remind her about the medicine.
Since the decease has cut down her daily activity, you should share her responsibilities voluntarily. Prepare meals for her or help her do the laundry. You must encourage her family members too, as they will be under great emotional and physical stress.