The Q: This is so very, very weird, but my fiance has an ex-girlfriend. It's not that he invited her or anything like that, but, I just received my RSVP's and she is coming as the guest of one of my friends! Talk about small world. I don't know what to do, because I know it shouldn't matter, but they dated for a fairly long time. I haven't mentioned this to anyone yet, except for my fiance, and he felt like it didn't matter to him if she was there. Should I ask my friend not to bring her?
The A: Wow! It IS a small world. The occasionally jealous woman in me would venture to say almost suspiciously small, but no one loves a cynic, right? Anyway, I think I wouldn't make a HUGE deal out of it, because it's not like your future Hubby invited her and it's not like she even came to show up through a friend of his. That said, totally worth a casual phone call to your friend to say, in your most forced nonchalant voice "O, so weird- I just got your RSVP and did you know that So and So dated (insert fiance's name here) back in the day." Chances are, he'll be as surprised as you are, and it's even possible that the girlfriend herself didn't realize whose wedding she was going to be attending. Your friend will probably ask if you are OK with him bringing her, and you need to be prepared to say either "Well, it is a little weird, but if it's serious between you two, what do I care?" or "No, not weird at all." or "Yes, too weird for words, leave her at home and I'll sit you with my cousin Clara." I would probably gauge my feelings based on his reaction.
If it so turns out that he did know about the sticky history, well.... you may want to write to me again. Kidding. I think if he did know, you may want to say that he should check with her that she doesn't feel awkward.
Ultimately, not knowing the players involved or their personalities, it's hard to totally guide you, but my step A would be the non-offensive phone call and possibly simply not caring. Happily it looks like all parties involved have found happiness.