My close friend talks about being suicidal and it's really start to grate on me. Is that mean?
Not necessarily. What part is annoying you?
A few years ago they stopped talking about suicide, but now they're bringing it up again nearly every day.
It's probably depression. Have you tried to get her help at any point?
I don't think she's actually going to kill herself. I think she just wants someone to talk to.
Since she seems to bring it up to you so often, maybe you should be the one to enact some action and get her help.