And by all means, please don't tell the suicidal person, "You'll go to hell!" My late grandmother said this to me when my late mother told her I was considering suicide. It didn't make me feel loved, and it didn't make me feel better.
When I was considering suicide, I would have been more helped to hear "I'm sorry things are rough for you. I love you and care about you," than to hear, "Don't you care about how you'd hurt So-and-So if you killed yourself? You're just running away from your problems."
Encourage the person to talk about what's going on, and remind her as often as necessary that you love her and care about her. If necessary, offer to accompany her to the doctor.