- Get at least one scratching post (or make your own!). If it's a vertical scratching post, make sure it's tall enough that your cat can stretch to use it. And make sure it's stable.
- Position the post near your cat's favorite sleeping spot, and/or near the furniture she likes to scratch the most.
- Cover the post in catnip or toys so that it's more attractive than the sofa.
- Reward the cat with a cheek scritch or a treat every time she uses the post.
- Don't hit her if she scratches the sofa. Just say 'no' firmly and relocate her to the appropriate scratching post, and reward her for using that instead.
- Talk to your vet if the problem persists.