I understand what you mean, my best freind is the same way. And sometimes I wonder why im her freind because she doesnt even react to my help. She just gets more and more depressed. But its because I love her. I care about her and I know that she does need me cheering her up as much as possible. It may be hard at times but hang in there. You have no idea how much you could be helping her. How much your help means to her. If you feel overwhelmed then find a freind to talk to. Call them or go out with them for lunch and that alone is suprisingly refreshing. But don't give up. You might be the only thing holding her together.