A friend of mine saw me at a party last weekend and excitedly told me she had received her invitation in the mail. She then introduced me to a guy she had started dating (started AFTER I sent invitations) and said, "This is ____. I guess he'll be my plus 1."
I didn't give her a plus one, because she was truly single at the time. We also have a huge group of mutual friends, so she wouldn't be there alone. I was caught off guard and it was right in front of him, so I didn't say she couldn't bring him. Luckily, I listened to Addie's advice on here and gave myself wiggle room with the guest list, so I'll be able to accommodate him. I just hope other people don't think this is a free for all.