Well. If she's making drama for attention, call her if you feel like it, tell her how special she is and how important. Listen to her, be a good lad.
If you don't feel like it and you sense like she's using you : ignore her.
Most girls who make suicide claims just cut themselves a bit or something lame like that. They probably just need some company.
You know the girl, you know the story.
If you think she is serious and that she will really try to end herself or cause herself serious harm you should call fir help
I did so with a ex long time ago. She was crying suicide. So I called her mother. Every went fine.