Gift

I'm sorry you have to deal with all of that, its a tough situation. I still wouldn't attend and your boyfriend shouldn't as well unless the bride apologizes. I know he's close with the groom but its not right for his good friends future wife to treat you the way she is. If your boyfriend doesn't want to go alone, thats on him but I sure has heck wouldn't go if someone treated me like that.

I probably wouldn't go if the bride purposefully went out of her way to include everyone but me. I'm quite shocked that they invited your partner and not you to the pre-wedding party. If you choose to go with your partner, I would just give a card with well wishes. Even if you don't, same thing.

I wouldn't go and neither would my partner if I had been treated like that. Has your friendship with the bride, or lack thereof, always been like this? You're in a group chat with a bunch of girls, how is your friendship with them? It seems weirder to me that you only found out about the pre-wedding event through seeing pictures and none of your other "friends" or your partner gave you a heads up about this event... Sounds like you may need new friends and maybe a new partner as well.

The fact that your partner was invited without you is rude, rude, rude, rude, rude.

Since your partner had no problem going to the co-ed stag party without you, I don't see why he has an issue going to the wedding without you. And I would tell him exactly that.

Don't contribute to the gift, and don't go to the wedding. If he can go party without you, he can go to the wedding without you, too.