I'm sorry to hear about both your problems and your friend.
It must be really difficult for you.
Most importantly, which i'm sure you are already doing, is to be there for your friend as much as possible. Sit down with him/her and be as helpful/supportive as possible. I also think your friend needs support professionally, too. It's a lot to deal with and obviously they aren't coping easily, so that's the best thing for your friend. Do you have depression of your own too, or is it mostly down to worry over your friend?

You really should get your friend help if that is what is going on in their head if they aren't already. You need to be sure of yourself that helping them by telling is what is best. My friends were there for me, and though I hated them for it then, they were assertive and didn't back off, and now I am greatful for them. You too need to e assertive with this, and get your friend help.

Now as far as that, as said above, is that the thing causing your depression? Is it your self esteem?

You need too tell someone in authority whats going on with your friend so that they call help them before its to late...please listen too POD- youth of the nation

First of all, I want you to realize that you can't blame yourself for not being able to cure your friend of her depression. It isn't your fault and there really isn't much anyone else can do to help one cure their depression, it is up to the person themselves. She has to be willing to get help for anything to help her. However, you can always encourage her to seek out help or make some changes in her life. Other than that though, the situation is out of your hands. Just be there for her, listen to her, and let her know how much you care about her.

As for you, what is it about yourself that you have low self-esteem with? If there is something you don't like about yourself, you have the ability to change it and better yourself. It may be more difficult to do so than you please, but just fight through it. Make yourself into the person you want to be, you are perfectly capable.

Do your parents know about your depression? If not, you should inform them. They can get you help so you don't have such a hard time dealing with it.
As for your friend, theres more then you think you can do.
I was in a similar situation a few months ago with my best friend, I was able to do a few things to help her.

1. I called a suicide hotline to try to get advice from another perspective. They helped me figure out ways to confront her about her issues.
2. I told her parents about her issues because she was to scared to. I'm not sure if you feel comfortable with telling her parents about what shes been going through, but its worth a try. Her parents can get her help so she doesn't want to kill herself anymore.