You could say that it's not really her it's a money issue that's why it's a smaller type shower and the place you're hosting it at isn't big enough for the list you've already written up. She may get upset, but hey it's your shower. You have every right to decide who or who doesn't come.
Tell her that everyone coming is bringing a $100 or more gift. See how fast she backs out, and if she doesn't you just got something awesome
Haha sounds so mean ^ but that could work
lol spritemystic that made my day