Names changed for anonymity. I have no idea what to do. I've been with Sam for months, and she's been friends with Diane for a long time. Recently (a few weeks ago), Diane asked us both out. We said yes, and that seemed to be okay.

Sam started dating a new person who was younger than her (she's 25, and the new partner, Lee is 19). Diane developed feelings for Lee, who didn't feel the same. Diane then became obsessive over the fact that Lee is 19, became suicidal, and after a particularly self-destructive night, decided she needed to talk to Sam. Sam, feeling very stressed from this, needed space. Diane felt unable to rest without speaking with Sam, so messaged her daily, even going so far as to drop some bread off at her house.

Diane now feels that Sam is irresponsible, careless, and selfish. She seems to also be talking about leaving the city.

I have no idea what I can do about this, or how to help Diane.