This is a challenging etiquette situation.
I'm having a destination wedding because my fiance and I are from different countries. I sent out invites asking guests to rsvp within 2.5 months of wedding date. (We had to provide final numbers 1 month out). I'm now 2 weeks from my wedding date and I just got a facebook message from an old friend in my home country saying that she will be coming with her 'plus one'.
I never invited plus ones - she is single anyway (only had her name on envelope.) Our wedding is small - 50 people - so I didn't want any randoms. Several other guests are young and single anyway. Even though I've barely had any contact with her over the last few years, I sent her a message a couple months back just to check and she was non-committal saying that she was 'looking at flights'.
What do I do? I find this so rude.