DesolateWaist I am so sorry for your situation. I hope you will find peace and the way ahead.
We had a baby and then tried for years for another. I was invited to a baby shower and went (and it was fine) but I would never ever expect anyone to attend if they did not wish to.
(We adopted after years of failed fertility treatment trying to have a second child. My lovely friends threw me a baby shower, it was great. But I know at least one friend there was possibly not going to be able to have a baby, and I am always sensitive of people who are in that position and of course there was no 'bump' putting in an appearance... so to speak.)
Weetabix re "I just don't get how a little tea party and a few pressies can be considered
'horrible', 'grabby', or against one's beliefs... I just find all these comments a bit bah humbug..."
Well, where to begin... it may or may not be a little tea party and in the OP's case she is being expected to help and organise and pay for it while pregnant. That is not on as she clearly does not want to do this.
'Grabby' may refer to the expectation that there is a present people will bring. I think it is quite common to take a gift, which is fine if you want to attend and want to bring something, but not fine for people to expect.
When someone says they don't believe in doing something it usually means they do not see the value of it, or in fact they see it as harmful or upsetting or inappropriate etc etc.
I am not wanting to put words in the OP's mouth but in my book encouraging someone to do something they are not comfortable with, in fact encouraging them to the point of trying to guilt them into it.... that is plain wrong.
The mutual 'friend' is not a genuine friend. I would ignore them. If you feel the need to send flowers or whatever, Captainkanga, then by all means do, of course. But you do not need to give reasons or whatever to other people.
In your shoes I would talk to the mum-to-be, explain your mutual 'friend' had been putting on the pressure and how uncomfortable that made you free. If she knows your history she will be totally understanding. If she does not understand (and knows the reasons) she too is not a real friend.
The reason I say to talk to her is because it is best to get things in the open because this other 'mutual friend' has made this an issue. Generally I didn't talk to pregnant friends about issues when we had fertility problems. When I did, when we were having problems before the conception of our dd, a friend was pregnant (her son is about 15 months older than my dd). She was full of the joys of pregnancy and I could not join in her joy. I explained and she felt I was being unkind.
We are over it now but, to be honest, people who have had no fertility issues just cannot really understand those of us who have had them (IMHO).
Good luck OP with your pregnancy and with it all.