Simple solution - get a chunk of plywood nearly the size of your box-spring, and place it under the box spring so it is what she will have to claw at. Heavy cardboard would work temporarily, but cheap plywood will be easier to find than cardboard that big, anyway.

The good news is that the damage is cosmetic, not structural, and that if you want it to look pretty again, a big chunk of fabric the right size and a heavy stapler will do the trick, without kitty-surgery or human angst! It's either blocking her access, or making under-the-bed off-limits.