Part 1: Vent
I had a feeling this would happen, but was really hoping it wouldn't. My FMIL offered to host a bridal shower for me and she's also helping to pay for the RD - awesome! Tonight, FI and I were talking and I just happened to bring up the bridal shower and asked whether or not he'd heard any news from his mom. He said "yes, I saw her working on the guest list today and she has already added several people". I was like, "Whoa! Already?" (FI and I are close to a final guest list, but have not completed it yet so I was really surprised that she was already making her bridal shower list).
So I went ahead and asked, even though I was afraid of the answer - I asked FI if she was only including people from the guest list and he said right away that he knew she wasn't. He said that he saw several ladies on the list that are NOT invited to the wedding!! I quickly informed him that we have a problem b/c of etiquette rules (he's not really up-to-date with etiquette, so I try to keep him informed

). I explained to him that if FMIL invites these people, then we're supposed to invite them to the wedding, but there's no way we can accommodate more people. He pointed out that she "plays by her own rules" - agghhh! - that's what I was afraid of.
I know he's right about her, so in the end, FI and I decided that we're going to talk to her about it together (soon), but we're going to try and be very gentle with her b/c we know she's stubborn and will most likely be PO'd about it. I also informed FI that if she refuses to follow proper etiquette, then I will be forced to decline her offer b/c we (FI and I) will be the ones who will look bad when we don't invite these people to the wedding.
Part 2: Referrals neededI'd like to send her a link to a website that explains why this is really poor etiquette, just so I have something to back me up - she might be more willing to listen. Other than the previous threads I've read about this, I couldn't find anything online about bridal shower guest list etiquette. All I found on Emily Post was "to invite friends, family & future in-laws" - well that doesn't help much. So if you know of a website link, please let me know so I can send it to her later - thanks!