How can you keep a cat from scratching the walls and door jams?

We have a cat that was mauled as a baby and only has 3 legs. The problem we're having with it is that it tends to scratch the walls and door jams as well as it's scratching post. We have tried putting aluminum foil on the places she scratches, but she just claws that up as well. Any ideas on how to train her not to tear our house up? Declawing is out of the question as she has to use her claws for the litter box and only has 3 sets!