<human>: Can you condense the text into a few key points?

My very good friend of 4 years has been suffering with depression ever since I've known her. 

I try to be the best friend I can and I listen to her rants and have long talks about trying to be optimistic and encouraging and give some advice, even if it is no help.

However, she refuses to talk to anybody else about her problem and seek help. Won't talk to her parents. Won't see a doctor. I know she wants things to change but is just incapable of putting some effort forth in the process and would rather just suffer.

It makes me sad to see her like this as I genuinely care about her, but at the same time there comes a point where I can only say or do so much that I just kind of burn out. After trying to help for 4 years, I come up with a loss for words and it can be frustrating.

I know depression is not something someone can just snap out of and it takes patience dealing with such an issue but at this point, I don't know what to do anymore. 

What is the best way to handle this?
<bot>: Friend has been depressed for years. I'm the only one who knows her issues. She does not want to seek help. I don't know what to say or do anymore.