If you cut the flight feathers you probably don't need to cut them shorter. I still suggest clipping both wings - it won't hurt anything to try - your goose may be too heavy to get airborne without both sets of flight feathers. Good luck!
I agree with chickentoes - try clipping the other wing as well. But she may just flap harder and still be able to fly... Let us know if it works! (or doesn't work!)