How do I help my depressed friend?

I have a very special and close friend to me who is going through a lot in her life. It seems like things have not been going well since her grandmother's passing in 2008. A lot of other negative things have happened since then: letting good friends go, constantly being taken advantage of because of her being nice to others, a sister who continues to put her through hell, bad relationships, and earlier this year, her mother was diagnosed with cancer. She has been very depressed for the last few years. I try the best I can to keep her in high spirits, but with all that's been happening to her, she is in a deep depression. I wish I could be there for her more, but unfortunately, she lives in Georgia and I live in Missouri. I feel like just calling her isn't enough, even though we talk everyday. She has even talked about running away from the problems, or worse than that, completely giving up on life and committing suicide. She believes in God, but says that she is so frustrated with Him for allowing these things to happen, particularly with what's going on with her mother, the only real family she has left. I don't know what else I can do for her. I am very worried about her mental state. If anyone has any advice on what to do, please offer. Any and all help is greatly appreciated. Thank you.