This happened to me too OP. An ex friend Emma and I were making plans to meet up. She suggested something with her gang and was really keen I join. I said yes great then within max two mins messaged and said I realised I was actually away with work that weekend. I suggested something else, no response.
A few days later I messaged and said let me know when you're free, I've nothing else in the diary except this work weekend so let me know when suits you and I'll join or else we can do our own thing.
She was busy with her wedding plans (and I couldn't have been more excited for her) and had given me the date and a plus one telling me to bring a friend if I'd no date. She told me the invitations would be coming soon.
When she didn't answer that second message I wondered a little bit didn't want to hassle her when she was probably busy. I continued liking and commenting on her posts.
Then I saw photos from her hen party. I had heard nothing about it.
Then her wedding came and went. I saw the photos on Facebook. The next day she blocked me everywhere. So I wasn't just an oversight, she was cutting me out.
Stranger still, her group of friends that I knew through her became very very awkward with me when they saw me around locally; we are talking extreme frostiness, pointed looks.
I was baffled but confident I had done nothing to this woman. I am not a drinker so nothing happened that I forgot.
I decided it was her loss.
This was about five years ago.
Bizarrely over the last year when I see her or her friends they are all OTT friendliness, really seeking out the opportunity to be warm and welcoming. I just smile, wave and keep walking. Whatever it is that I've been forgiven for is in their own heads.
I think you should leave your friend to it. Her behaviour is cruel and immature.