I've got a slightly different perspective. I hope I'm not flamed...
My best friend has been struggling to get pregnant for some time. I was always of the school of thought that where one person has fertility struggles and the other is pregnant, it should be 100% about sensitivity to the person with the fertility struggles. After all, the struggling person is the one who is suffering mentally on a daily basis, while the pregnant person has everything the other person dreamed of and can celebrate and chat about the pregnancy with other people.
Then I got pregnant... and it is much harder being in this position than I expected. When I realised that I was pregnant, I was immediately anxious about the impact on my best friend, it took over my thoughts and upset me a lot. I dreamed about her, I cried in fear over what it would do to our relationship, I thought and thought again about how I could most sensitively deliver the news. I ultimately decided the best way to tell her was by text. She did not respond to me for a week. I was a nervous wreck for that week, and really upset that I was hurting her so deeply.
After that week, she warmly congratulated me. This meant the world to me - not because I thought she was happy or okay, but because I meant enough to her for her to want to do that in such difficult circumstances, and because it made me hope that our friendship was not over.
We've had a few bumps in the road. We have definitely seen less of each other, but she has not avoided me entirely. I never mention the pregnancy. There was a period of a few months when I was really struggling and thought I might lose the baby. It was really difficult for me to see her and act normally when she knew nothing about that. Yes I had support from others, but it was harder than I had imagined to be going through something so difficult with no support at all from my best friend. It felt hard to think that if something were to happen to the baby, part of her might be relieved.
Now, later in the pregnancy, when we do see each other she will of her own volition very kindly ask me how I am feeling or even express excitement. I know how incredibly hard this is for her. I love and admire her so much for having the grace and love to do this.
I suppose what I'm trying to say is that it's not quite as black and white as it might seem. People have zoned in on OP's comment that her friend has said she should be happy for her, but seem to have missed the fact that OP completely ignored her friend for her entire pregnancy, then turned up and was unable to put on a good face when she finally did see her friend. I don't suggest for a minute that it would be easy to put on a good face in the circumstances. Just that to me, it sounds like her friend has extended a good deal of tolerance and understanding already. If my best friend totally ignored me for my whole pregnancy, then made a scene when she finally saw me and my baby, I might have understood it, but I would have found it very difficult, anxiety-inducing and hurtful, and it would likely have permanently damaged our relationship. As it stands, we have come to a sort of middle ground situation where we both try to be sensitive to each other, and I think - hope - our friendship will escape unscathed.