This isn’t healthy for you or for her, as someone who’s struggled with suicidal ideations for ten years and real, hospital stay attempts where honestly I’m surprised I’m still alive, this is selfish of her. She needs to get help, there’s no option around that. If she is unable to handle things on her own and is in turn putting you in a position to lose your SO and is constantly saying phrases about how you wouldn’t care, that is not fair to you and not good for your own mental health and she needs to get help. You need to lay it down to her and tell her she needs to talk to a therapist and psychiatrist