Well now I know that reason why I didn't just throw in the towel and completely give up on my friendship with M even though parts of me definitely wanted to, to save me a butload load of guilt.
Monday a letter arrived from M addressed to D.G. I was a good person and did not open D.G.'s personal mail, but I had to hide it so it would not torment me. D.G. finally read it Tuesday at work and brought it home for me to read too. M lied to D.G. on the phone last week when she said things were fine. It turns out that M is probably as messed up as I am, but possibly more in some ways. Without going into too many details, she ended up with severe post-partum depression, her husband got hurt and then lost his job (I knew about the hurt part) and is still unemployed so they are broke and their marriage is on the rocks too.
I know that it's impossible to reach out to other people when you are in the middle of a major depressive episode. The fear of being rejected completely outweighs the potential benefits. I also know that D.G. and I had over 13 years together before we lost our son and I got depressed, including a previous depressive episode, so we have a big foundation to work from if we are going to continue to make it through this. M and her husband have only been together for the last 3 and a half years and this is the first major challenge they have faced together. (Not that 3 years together isn't enough time to build a strong relationship and not that 13 years together means you can get through anything.) So I now understand at least part of why she wasn't there for me after she had her baby and no longer had to avoid thinking about me in order to not freak out about the possibility of her baby dying.
I guess this means the ball is back in my court now. If only I had the smallest clue about what I am supposed to do now.