Curtains answer three needs at once
To your cat, a curtain is not decor. It is a climbable surface that moves interestingly, a scratching texture that grips her claws, and a ladder to the highest vantage point in the room — the curtain rail, with its view of the whole territory and the window beyond. Cats are vertical animals; the drive to get up high, survey from safety and scratch on a surface that yields is normal, healthy behaviour looking for an outlet. Kittens and young cats climb curtains most because they are light enough for the fabric to hold and energetic enough to try everything, but an adult cat who starts curtain climbing is usually reporting that her legal vertical territory is missing, occupied by another pet, or in the wrong place.
That diagnosis decides the fix. You cannot train the need away, and you do not need to. You need the need met somewhere better, positioned so well that the curtain loses the comparison.
Put the legal mountain where the illegal one stands
Place a tall, unmistakably stable scratching post or cat tree immediately beside the curtains she actually climbs — not across the room, not in a different room where a better-behaved cat might use it. Location is the whole game: cats scratch and climb where they already want to be, which for your cat is that window. The post should reach high enough to offer a perch at or above the height she gains on the curtain, have a scratching surface she can stretch fully against, and not wobble when she launches at it. A post that rocks once will be filed as unsafe and the curtain, which at least behaves predictably, will keep the job.
Make the post pay from the first day: run a wand game up and over it, place treats on its perch, reward any scratch delivered to it, and position the perch to keep her street view.
Take the fun and the fabric out of the curtain meanwhile
While the post earns its reputation, tie curtains up out of reach or swap them temporarily for a blind. A curtain that cannot be climbed stops rehearsing the habit daily, since each successful climb is self-rewarding practice.
Avoid spraying or shouting as the main strategy. A cat sprayed mid-climb can panic, slip and injure herself, and deterrents alone leave the height need unmet, so the behaviour resurfaces on furniture or shelving.
Maintain the climber, not just the furniture
Keep her nails trimmed so that if she does make one attempt, her claws catch less fabric and she is less likely to hang painfully from a snagged claw — a cat stuck dangling by one claw is a genuine injury risk. Give her climbing an energy outlet as well: a daily play session that includes vertical chasing, up over the post and down again, spends the athletic drive that otherwise funds curtain expeditions at dawn. In multi-cat homes, check whether the curtain window is contested territory; a second post by a second window can end a queue that one cat was solving by climbing fabric instead.
If climbing suddenly starts in a previously settled adult cat alongside restlessness, weight change or appetite change, mention it at her next veterinary visit, since a new drive to be restless and active can occasionally have a medical thread worth checking. With KinsLe Care Teams, the daily post play, perch treats and nail-check duties can be split across the household and marked complete with a timestamp, so the curtain's replacement gets the consistent promotion it needs to win for good.