You cannot train a cat out of scratching, and you should not want to. It is maintenance, exercise and communication all at once. What you can change is where she does it.
Three things scratching does for her
- Claw maintenance. Dragging the claws down a surface pulls off the worn outer sheath and exposes the sharper layer underneath. This is not optional grooming, it is how the claw works.
- A full-body stretch. Watch a cat scratch after a nap. She is stretching the whole chain from shoulder to spine, and the scratching surface is what she braces against.
- Marking. There are scent glands in the paws, and the visible marks are a signal too. This is why the most scratched spot in the house is usually next to a doorway or the sofa arm that faces the room.
Why she picked your sofa specifically
She did not pick it to annoy you. She picked it because it wins on the four things cats actually care about:
- Location. It is in the room where the household lives, usually near where she sleeps or where people come and go.
- Stability. It does not wobble or slide when she puts weight into it. This is the single most common reason a cheap scratching post gets ignored.
- Texture. Woven fabric shreds satisfyingly and gives the claws something to catch.
- Size. She can extend fully against it.
If the scratcher you bought is lighter than a book, sitting in the spare room, and made of something that does not shred, you have not given her an alternative. You have given her a decoration.
What actually redirects her
Put it where the problem is, not where you want it
The alternative goes right next to the spot she already uses. Not across the room, not in the hallway. Once she is using it reliably, you can move it a short distance at a time, but start by competing on location.
Weight matters more than height
Whatever you give her has to stay put when a full-grown cat leans into it. A flimsy post that tips once is a post she will never trust again. Solid wood, a wide base, or something you can anchor.
Match the direction she already scratches
Some cats are vertical scratchers - door frames, sofa arms, the side of the bed. Others are horizontal - rugs, carpet, the arm of a chair lying flat. Watch which one she does and provide that. Buying a tall post for a horizontal scratcher is the most common mistake in this whole category.
Make the new surface interesting on day one
Catnip, a treat placed on it, or a wand toy dragged across it. You are trying to get the first few uses. After that the surface sells itself, because it does the job her claws want done.
Make the sofa boring at the same time
Double-sided tape or a throw over the arm for a couple of weeks, while the alternative is doing its work. Remove it once the habit has moved. Punishment does not work here and makes her wary of you rather than of the sofa.
Keep the alternative easy to use
Once she has chosen a better surface, keep it stable and in the same place. Refresh it when it is worn out, and keep an option near each area where scratching tends to happen.
A scratcher will not stop scratching, and it should not. The goal is to give her a reliable place to do it that is better than your sofa.
When scratching is telling you something else
A sudden increase in scratching, or scratching in new places, can follow a change in the household - a new pet, a move, a new baby, a change in routine. If it comes with other changes like litter box problems, hiding or over-grooming, it is worth a conversation with your vet rather than a new scratcher.
This is general care information, not veterinary advice.