I was in a similar position a while ago. I met my friend when we were both doing IVF at the same clinic at the same time. Sadly, it didn’t work out for either of us and she has frozen embryos ready to go. I left my partner and ended up falling pregnant naturally with a new partner. When I told my best friend I was pregnant, it was before most other people and via message. I acknowledged how she will be going through all of the emotions and reassured her that I didn’t expect a reply any time soon and for her to take as much time as she needed. I explained the reasons for texting (so she could deal privately and didn’t feel the pressure to put on a brave face) and told her that I would understand if she felt the need to take a step back in our friendship although this isn’t what I would want. But I understood if she needed to. And that she could be as involved as she felt comfortable. I was very lucky that, although my best friend was sad for herself, she was over the moon for us
It’s very tough but at the end of the day this is happening whether she’s happy about it or not, you can’t protect her feelings unfortunately. You will have to tell her in a delicate way but be direct.
Just to look at it from another angle, if you weren’t the one who was pregnant and she was, would you be happy for her? If so then you should expect the same behaviour from her. But by the sounds of it she’s quite petty and demanding. So if she doesn’t see it that way, if she isn’t happy for you, is she someone who you want as a friend? I know it isn’t the same but a friend and I got pregnant at the same time and she messaged me a couple weeks later to say that she’d lost the baby but she was still so excited for me and didn’t want me to feel like I couldn’t message her about my pregnancy. In Jan we are all going away for a weekend with another friend who’s pregnant. She’s a blooody amazing friend, and I hope it turns out yours is like that too. I think to help her organize you should tell her as soon as possible, but maybe just decide beforehand for yourself how you will feel/react based on her reaction. Then it shouldn’t turn into a big thing.
Really difficult with things like this as can see there’s multiple issues here. The friendship may not survive from the sounds of it - even though of course you’ve done absolutely nothing wrong. You can’t go on the hen do and that’s that I guess and hopefully you can still celebrate another way before hand in good time and make the wedding. But how she takes it all, I guess isn’t something you can control. Very difficult all round with situations like this xx