My friend is depressed.

I have the one close friend I had for over 13 years. She was the sun in my world, my best friend. Just a couple hours after we called she started to doubt a lot of things, like whether anyone cares about her. That was all because some dumb b!tch thought it was a good idea to tell her a bunch of crap that didn't even make sense, cyberbullying. A couple of hours after my call she told me she wanted to kill herself. At the time I thought she was just making a very bad joke, so I laughed it off at first, but it wasn't funny anymore. I contacted all her friends and they said that it wasn't a joke and I should do something before she kills herself. I really have nothing more to say, please help me.