I just found out that my mom is trying to do what I call "subbing guests" for my wedding. To explain, when I asked her to give me a list of people to invite, I specifed that she should limit it to family and friends of hers that I actually know. So when my mom found out that one of her unmarried friends that was on her list wasn't planning on bringing a guest to the wedding, my mom asked this friend to bring another one of her (my mom's) friends that neither this friend of hers of my fiance or I know. When I found out about it, I asked her about it and told her that I didn't think that was right of her to do that. I explained that even though we budgeted for singles to bring a guest, if they decide not to, that will save us money and that we could use it for spending money on the honeymoon or other things we might need. She just didn't understand that concept, so she got mad at me and that started an argument. At one point I asked her whose wedding this is, hers or mine. I'm concerned that she doesn't understand the principal of my fiance and I being the ones that should decide how we want to spend our money for the wedding, and that we don't want to spend our money on her friends that we don't know.
To give you some background on my family situation, which might help you better understand...
My mom and dad divorced when I was 4 and there are still some hard feelings between them. My dad comes from a large family and my mom comes from a very small family and for some reason my mom doesn't like that a large portion of the people at the wedding will be relatives from my dad's side. This is my 1st wedding and my fiance's 2nd. We are both in our early 40s and have good jobs but, like most people have a lot of bills and don't have a ton of extra money right now. My dad and step mom earn a modest living but they are contributing about 30% of the total cost of the wedding and honeymoon (including airfare and hotel only). My mom is retired and she said she couldn't afford to help much with the wedding, but she did pay for my dress, which I really appreciate. So my fiance and I are paying for everything else (about $70%). He and I have been putting money aside since we moved in together in September and we're getting married in June, so we only had 10 months to save all of this cash for the wedding.
I'm just wondering if there's any kind of etiquette out there, or anyone's personal opinions on the situation about my mom "subbing guests." My mom just doesn't understand why what she's trying to do isn't right. I want her to understand why it's wrong, and also want to make sure that other unexpected friends of hers that I don't know and weren't on her invite list don't show up at the wedding. Help!?