Long time lurker, new member here that could really use some advice. Backstory is my Dad is paying for the wedding (he and mom and married, but have a rocky relationship and keep their money separate). When we first got engaged we asked my parents and FILs for guest lists, came up with our own, talked budget with Dad before looking at venues. My mom would not give a guest list no matter how many times we asked. The other lists totaled around 100 and we asked repeatedly if my mom would need 100, 200, how ever many she would need so we could start looking. Well she said 100-125 would be fine, and she and Dad helped us find a venue that would hold 225 comfortably with vendors, that they absolutely loved and was well within budget.
Here's the problem, after we signed contracts and put down deposits she comes up with a guest list of around 200, many people we don't even know. We convinced her to narrow it down a bit and we got to 240 total (all lists) and sent save the dates. However, now every time we talk about anything related to the wedding she brings up how unhappy she is she couldn't invite everyone that she wanted to, that the room is too small, and that she is upset she had to cut people off the list. She's unhappy we want an adult reception and is hinting that she will tell people they can bring their children even though STDs were addressed only to the adults and we did not include children in the final count.
How do I handle this? I can't keep having the same conversation with her about how she wants to invite everyone that she wants. We've offered to look for another venue, but my dad refuses because he loves what we all together picked out. How do I get to see she's missing all the other planning she wants to be a part of because she's hung up on this? I don't want to have this affect our relationship in the future but I am getting so frustrated at havinag her bring this up every time we have to talk about something wedding related. I would love any advice you wise women have.