So. A few weeks ago, we saw FMIL and gave her two StD magnets, one for her and one for FI's grandparents. We didn't mail them since we were seeing her anyway, and she sees the grandparents regularly.
Next time we saw everyone, we asked grandparents if they got StD. FMIL interjected that she had seen an old family friend (mother in a family of four) shortly after we gave her the Stds, and she gave the one meant for grandparents to said friend, who is not, in fact, on our guest list.
My response: It wasn't FOR them. Her response: I know, but she asked about FI so I gave it to her, it doesn't mean she thinks she is invited! FI: Then what is she saving the date for? FMIL: (silence).
We were both irritated about it, but I guess we just forgot about it until FI recently ran into the husband of the woman, and he mentioned our StD magnet is on their fridge.
We know the rule, everyone who gets an StD must get an invite, but this isn't something we meant to happen, and we can't afford having this family at our wedding. We already hacked our guest list to pieces until only our families remained, no favors, lots of DIY, no frills. There is not an extra $250 in our budget for them.
Short version: FMIL gave StD to a family she knows without checking if they were on our guest list first. They are not, and we don't think we can swing paying for them. What should we do?