How do we stop this? I am baffled

There are sites online that maybe able to help or contact one of the nurses at the vets. Good luck.

I think that cats like to go back to the places they have scratched because they scent-mark them by scratching. Could you try one of these sprays that disguises the scent on the area of wall she is scratching to try to dissuade her?

I speak from the experience of having a very nice sofa entirely ruined, a few years ago!

I have no idea why your young cat is doing this, but I have an idea for hopefully stopping her from scratching the wallpaper. Would you consider screwing a piece of perspex over the favoured area? This would feel uninviting to the cat and would be likely to break the habit.

Can you stand a piece of furniture in front of the place? Perhaps a small bookcase?

I successfully used some of these double-sided sticky strips on my leather sofa, almost invisible in place. The cats haven't touched it since application months ago. Obviously the strips may damage your wallpaper on removal as they are very tacky, but I found I could smooth the ragged bits of leather when putting in place. Good luck!
cat scratch strips

Have you checked her claws? One of my cats chose a specific doorframe to scratch, and I couldn’t get to the bottom of why. At his vet check I asked, and he turned out to have an ingrowing claw, so he apparently picked that particular place because it was exactly the right angle and roughness. I didn’t even know they could get ingrowing claws, but once it had been clipped he stopped.

I sprayed my cat with a tiny drop of water, and that is all it took.

He wasnt in a hurry to have that happen again.

I could just say "excuse me!" and he stopped.

My daughters cat used to do this in 2 places and nothing she did would stop him. She eventually bought wall mounted scratch panels. Not pretty but better than ripped walpaper!

When we had our kitchen redecorated recently we abandoned thoughts of wallpaper and had it painted. Milo had two main areas where he enjoyed ripping paper off. Usually after sharpening his claws on his scratching post. He also scratched the lounge carpet and my whicker sewing carpet. Our other cat Ripley, doesn’t scratch anything! So the way forward is paint!

MissAdventure

I sprayed my cat with a tiny drop of water, and that is all it took.

He wasnt in a hurry to have that happen again.

I could just say "excuse me!" and he stopped.

Daughter has a cat, she also sprays water, says that works a treat.

Had cats all my life, but only one that scratched the wallpaper, I have no idea why but eventually had to remove the paper and paint the wall as nothing would stop him from doing it.

Our last cat was impervious to water sprays. She learnt to close her eyes when she saw you coming and just carried on being naughty.

We had a dog that used to try and dig in a corner of the hall, pulling the carpet back and still digging. No rabbits were found, although we did have a cellar.

However, is this a solid stone wall or a cavity wall? We once had bats in a cavity in one house and in another a squirrel ran up and down the cavity until we found where it was getting in.

Wildlife loves us. ?

Go for the "big guns" and open the door of the cupboard where the flea spray is kept.

I shall try the cat sprays, thank you.

Water will not work - she loves it! And the problem is not her claws - I check them regularly as she has an extra claw and toe on each forepaw and she manages to keep them all the right length as she and Tigger have branches to use as scratching posts. Trubel having watched me file my nails proffered a front paw when there was a claw she was having a spot of bother with and lets me file it for her! But thanks for the thought.

The trouble is we never see her do it, only the results!

The hall measures just over a metre in width, so no, putting furniture there definitely won't work,

We had a cat that used to scratch at our bedroom door so I stuck a lemon air freshner on the bottom of the door and that stopped him.

Rub some citrus peel on the spot. Cats don't like citrus smells.