NTA. I'm sorry you're dealing with social anxiety and PTSD. That sucks. Props to you for going to the bachelorette party to support your friend.

The bride seems unkind. If the whole party was concerned you were sitting on the floor, perhaps they could have spoken to you about it then? I would have been concerned about someone so withdrawn, even if I didn't know them well.

That the bride had time to reflect for two days, then reached out to you to deliver the Collective Judgement that you were So Totally Awkward, based on their misreading of your phone (or maybe a gossipy lie about your phone)... okay. These people are terrible.

You used your limited energy to be there. You say the bride's partner is a lifelong best friend, so you clearly put work into your relationships. I am sorry that consideration wasn't returned to you.

Don't let the muggles get you down.

I would leave this wedding party but that's up to you.