[6t]

I guess she doesn't want you riding pillion then
The alloy wheeled seats fit the spoke wheeled bikes and vice versa.
Two things to watch out for. The later efi bikes have a different seat pan to clear some of the efi electronics. Not an issue for fitting an efi seat to a carb'ed bike but the other way around can be an issue.
Also if your girlfriend is of the petite variety as well as being cute bear in mind that all the other seats are thicker than a stock efi Bonneville seat and therefore the distance to the ground will increase.

 

[6t]

Ok, so posts #5 and #9 here suggest that the older Thruxton seat pan won't work on EFI bikes, but post #8 says the opposite. So which is it? I'm looking at this seat for my 2013 Thruxton, which the manufacturer says is based on the carb'd seat pan, which it claims will work on an EFI Thruxton.

Pardon Our Interruption...

All air cooled seats are in theory interchangeable because the frames are basically the same. The issue is that efi bikes have electronic components under the seat that the carbed bikes don’t so the efi seat pans have a recess to clear those components
Sometimes if a carb seat is fitted to an efi bike the pan can press down on the electronics and cause an issue. Usually with a heavier rider when they are far from home.