I agree with the others saying it's postpartum depression. It's not something that goes away on it's own, and if she's not willing to voluntarily go to therapy you may want to reach out to online groups of people who suffered from or lived with someone who suffered from PpD. They may have some solid advice on how to approach your fiance. The challenge here is that you've only known her 2 years. That's a very short time, so your baseline of who she is outside of this depression is skewed to the honeymoon period in the beginning of the relationship. That being said there was something that attracted you to this woman to start with and I wouldn't suggest bowing out immediately over this, though that's not to say not to consider the option in the future. Also I'd suggest easing up on enabling behavior on your part. You can't maintain the family all by yourself and what you call patience is actually enabling. She gets away with being depressed because you're buffering the consequences. The consequences are hard and bitter and difficult to deal with but they are necessary to help her see the light if she's ever going to choose to. Best of luck sir in whatever decision you make.