Replying to Depression

My girlfriends brother is dying of cancer and hes only 16. She is really close to him. She has gotten really depressed to the point that she doesnt know what to do with herself. She doesnt want to get out of bed in the mornings and finds no purpose in life anymore. I have done everything I can do to let her know that I am here for her and that she can talk to me about anything and that I was there just to listen, but nothing seems to help. I dont know what to do. If anyone has been in a similar situation I would really appreciate some help.
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Worrying is like a rocking chair. It gives you something to do, but in the end, it doesnt get you anywhere. Write that down.