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When Karin took on Coco, about 6 months ago, though she was provided with nice sleeping arrangements, Coco insisted of sleeping on her fairly old sofa, so Karin decided to buy a new one, keeping the old one for Coco, and wouldn't you guess, she now eschews the old one and sleeps on the new sofa!
Perhaps the barricade may be the only way, I was thinking that there might be some kind of herb that dogs don't like the smell of - I believe cats don't like the smell of oranges for example, but I've never put it to the test.