I suggest 2 things
1) be there for her
-sometimes they just need someone to help them out and support them
2)get her a hobby
-something fun like art class or even the Ning
First off, your friend, while not in her normal mind, believes she is thinking rationally. Physical pain releases endorphins that make the emotional pain feel better, but it is not a healthy coping mechanism.
Second, I agree with Mod Ding, if she's a suicide risk, you need to tell someone who can help her. She's not in her normal state of mind, and needs professional help, even if she doesn't want it.
I want to add that you shouldn't let yourself get burnt out. Suicide risks can be a big drain on the people who care about them, and you need to respect your limits. You're no good to your friend if you allow yourself to be stretched too thin. Respect your own psychological health. If you need to, talk to a counselor about the stress you're facing with your friend. It's one of the best things you can do for yourself if you're struggling with a friend who is a suicide risk, and they will be able to point you to good local resources for your friend as well.
That said, sometimes all they need is someone who will listen to them. If you can be that, great.