I'd talk to her.......I attempted suicide when I was 15, and I didn't tell anyone I was planning to, I imagine if I had made a note and someone found it I to would have probably either said it was a joke, or that i was just writing poetry or something. I mean I can't be sure if it really was a 'joke' or not but with suicide its better safe then sorry.
But yeah if you talk to her about your experiences that might help, just be careful not to indicate she's wrong for feeling this way or anything like that.....otherwise she might not be willing to listen because she will just feel like you don't really want to help.
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We won't go back.