I'd let her on the couch and see how she reacts, and go from there. Some cats don't even like the feel of leather on their paw pads, so you may not even encounter a problem. I agree with what others have posted above about trimming their nails. I trim my cat's nails about once a week or more if needed, and that really helps. If the nail has a blunt edge, it's harder for it to puncture something. I have never tried Soft Paws, but I have only heard great things about them. I know you can get them here at PetSmart. I use the squirt bottle trick too, mostly to keep the cats off the coffee table while eating in front of the TV. I spray as little as possible (a few drops works!!), never near the head (always on the hips) and am finding now that if I just pick up the bottle and shake it, they know what that means and jump down. And I'd try to make sure there is a scratching post in the same room as the couch. That way, the kitty has somewhere else to get a good stretch in if he needs to, and doesn't have to go far.

Good luck!