Was the couch second-hand? If it was, she might havae smelt an old cat who used to pee onit.

I have heard of cats peeing on the furniture before, but it was always either second-hand furniture that probably had been peed on before or cats living ina houses with bad catmoms - negelcted, abused or overcrowded, very stressed cats.

Unless she was the first cat to pee on the couch, I wouldn't expect a problem, but if there has been a precedent I would invest in a good plastic mattress case.