Let me preface this by saying I love my mom. She is an interesting and eccentric person and I let her get away with a lot because we are very close and she has some medical issues that make me want to make the most of the time I have with her.
That being said, she's very passive aggressive and kind of does whatever she wants. My FI and I put together a list of family and friends that we were inviting. We then asked. His parents for a list of their friends. They invited maybe 20-25 people. We told my parents they could invite 40 people because they have a larger friend group and that would bring us to a max of 150 people. They came back with a list of almost 100 must haves, plus a B and C list. After a lot of negotiating, we decided that since we were having the wedding at their house, they could invite the extra people if they paid for the extra seats (food, tables, chairs, bigger tent if needed, etc). My dad reluctantly agreed.
After we sent out our save the dates my mom texted me saying her friend asked if her adult daughter could come to the wedding. I begrudgingly obliged because the girl and I knew each other in middle school, (though we haven't spoken since then and I remember her being quite mean time me).
Then, 3 weeks prior to the wedding, she asked if I had invited a cousin of hers and his new wife. Now i had given my parents the guest list multiple times so they would know who was invited and who was not. At no point did this cousin come up. Apparently he brought it up to my mom and she then asked me if he and his wife could come. I again obliged because I had invited both of his sisters and not inviting him was an oversight on my/my parents part.
Now we are less than 2 weeks away from the wedding. Everything is set. We've given our final counts. We received a rsvp card from another of my parents friends saying that not only are they coming (which we knew about) but their adult daughter is coming as well. It turns out that they also asked my mom if their daughter (who I do not know) could come and my mom said YES without asking or informing me. At this point we have no room at the tables. We already have people seated at the ends of the banquet tables. I am upset with my mom for thinking that this is acceptable behavior and I am upset that her guests think they can bring whoever they want.
So so what do I do? Am I in the wrong here? Did I bring it on my self by allowing her to invite a few more people? Do I call the lady and tell her that her daughter can't come? I am at a complete loss as to how to handle this. Is it worth causing a fuss or should I just let it go and see what happens? Advice please!!