Suicide is a drastic action for anyone to take. It is usually the result of an immense, inescapable pain someone has been feeling for sometime; death seems like the only way out.
Now, I'm not going to say that I'm an expert on this. But if I were you, I would comfort her as much as possible, and make it abundantly clear that I'd be there for her. I would try to dig into her, and understand why she attempted suicide. I would do whatever I could do to maybe solve the problem, or at least make it less painful. Whatever you do, do not abandon her.
Ultimately, getting professional help would be optimal.