Here's the background, please give me your honest opinion.
I'm hosting a bridal shower for my FSIL. For some reason my mother thinks that I as 28 year old women am unable to do this event on my own and has decided that she will help me.

This is a family event; my grandmas, aunts, cousins etc are invited. The bride and groom will be moving across country after the wedding because my brother is stationed back East.
Okay, here is where I need your opinion: I was talking to my mother about final details of this event and I told her that I had the invites just about done and I had planned to drop them in mail today. She asked what I decided to do as the "theme" and I told that I had decided to just not have a theme (so no kitchen shower etc). My mom informed me that she and the bride were talking and that they think it is best to include on the shower invites that this is a "gift card" shower. I told my Mom that I thought that was totally tacky and that I guess I am "old school" when it comes to things like this because I dont think you tell people what they can and cant buy a person as a gift. In my mind I dont think I would attend a shower if that was was the theme. I understand that they are moving and that they will have limited space for things, but why not do what everyone else does when they get married- if you get something that you dont want you return it for a gift card.
Please weigh in and give me your opinion, my Mom thinks that I'm out of line for throwing a fit about this. So, I need to have someone's outside view.