How do I handle this situation?

[adpiucf]

I think when you meet, you should do the introductions and say, "Hi, just to get it out of the way, and just so you know... We already don't like you. You have come off as a complete psycho and we have zero interest in accomodating your insanity. I thought it would help for you to know that you've really done a bang-up job of portraying yourself as someone that none of us could ever hope to be friends with. Well, thanks for coming all this way! Do us a favor and don't talk to us. For the sake of the bride, we're here to have fun and show her a good time. But we really don't like you. Kthx!"

Seriously. Throw it right back in her face.