Nobody here at works agrees with her either, but nobody is really saying anything disagreeing with her, otherwise she'll be all kinds of ticked off and it wouldn't be a fun place to work for a few days.
She got all bent outta shape when his parents had their 50th wedding anniversary. They took their kids (3 of them), their partners (2 are married and these two had just been dating 3-4 months) and their grandkids out to dinner and picked up the tab. After dinner, they went back to the parents house and the parents had invited several of their friends over for cake and visiting. She was ticked that they never said anything about having her kids over.
Glad to known that we aren't the only ones who think she is a bit extreme in her idea.
Oh yeah, Miss Thing is a piece of work. Does she realize just how expensive it is to pick up the tab for that many people at a restaurant? Last year I decided to take my siblings, their kids and my dad out for a casual crab feast buffet. I spent around $500. That was for 12 people. You don't just tack on an extra 6 people lightly for those things. Especially adults you barely know who can darn well pay for themselves.
Also, how fair was it that Grandma & Grandpa had to foot the bill for their own 50th Wedding Anniversary party? Seriously. When my parents celebrated their 40th, my siblings and I paid the bill for the party. In fact, I don't believe there was ever an anniversary dinner we didn't pay for since we were teenagers. That's one day you can show your appreciation for your parents and take care of them.
Girlfriend has major entitlement issues. Grandma is trying to offer some casual gathering times for her son and minor grandchildren. She's being welcoming enough to include the girlfriend as well. I bet if you asked Grandma she would confess girlfriend adds far more drama to her life than she'd like. But you don't chose your children's romantic partners.
In my own experience, invitations are for households unless there's a special requirement of "kids' party" vs "adults' party". Once someone grows up and establishes their own household, they get their own invite.
Now I have extended an invite to a grown cousin through their parents when I didn't have the cousin's new address, but I made that clear in my invite. Usually by saying "Please let X know they are invited too. We'd love to see them."
I do a lot of casual gatherings too. Usually by text message, phone call or e-mail. It is usually "Hey wanna hang out this weekend?" Then we figure out what to cook up depending on the group size. I stock up on frozen pizzas and pre-made frozen meats. Worse comes to worse we do Subway or fire up the grill for hot dogs and burgers. As soon as the kids hit their teen years we expected they'd accept or decline depending on what other invites they had going. Their parents are basically there for transportation.