In all honesty, Hacker News is the last place I would be looking for advice when it comes to serious matters like depression when there is a life potentially on

In all honesty, Hacker News is the last place I would be looking for advice when it comes to serious matters like depression when there is a life potentially on the line. If I were you I would seek the opinion of a psychiatrist or doctor who can help you better understand the illness and provide the best course of action for helping. The best thing you can do in your situation is be supportive and patient for your fiancée. I hope everything works out for you. Has your fiancée seen a medical professional about their depression, if not, I strongly advise you get them to a doctor ASAP.